Convert string16 to use base namespace.

TBR=sky

Review URL: https://codereview.chromium.org/109233002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239538 0039d316-1c4b-4281-b951-d872f2087c98

201 files changed, 948 insertions, 902 deletions

diff --git a/chrome/browser/enumerate_modules_model_unittest_win.cc b/chrome/browser/enumerate_modules_model_unittest_win.cc
index df4850a..d7bed9c 100644
--- a/chrome/browser/enumerate_modules_model_unittest_win.cc
+++ b/chrome/browser/enumerate_modules_model_unittest_win.cc
@@ -211,8 +211,8 @@ TEST_F(EnumerateModulesTest, MatchFunction) {
 }
 
 const struct CollapsePathList {
-  string16 expected_result;
-  string16 test_case;
+  base::string16 expected_result;
+  base::string16 test_case;
 } kCollapsePathList[] = {
   // Negative testing (should not collapse this path).
   { ASCIIToUTF16("c:\\a\\a.dll"), ASCIIToUTF16("c:\\a\\a.dll") },
diff --git a/chrome/browser/enumerate_modules_model_win.h b/chrome/browser/enumerate_modules_model_win.h
index 51243d1..249cb82 100644
--- a/chrome/browser/enumerate_modules_model_win.h
+++ b/chrome/browser/enumerate_modules_model_win.h
@@ -78,17 +78,17 @@ class ModuleEnumerator : public base::RefCountedThreadSafe<ModuleEnumerator> {
     // The module status (benign/bad/etc).
     ModuleStatus status;
     // The module path, not including filename.
-    string16 location;
+    base::string16 location;
     // The name of the module (filename).
-    string16 name;
+    base::string16 name;
     // The name of the product the module belongs to.
-    string16 product_name;
+    base::string16 product_name;
     // The module file description.
-    string16 description;
+    base::string16 description;
     // The module version.
-    string16 version;
+    base::string16 version;
     // The signer of the digital certificate for the module.
-    string16 digital_signer;
+    base::string16 digital_signer;
     // The help tips bitmask.
     RecommendedAction recommended_action;
     // The duplicate count within each category of modules.
@@ -199,10 +199,11 @@ class ModuleEnumerator : public base::RefCountedThreadSafe<ModuleEnumerator> {
 
   // Given a filename, returns the Subject (who signed it) retrieved from
   // the digital signature (Authenticode).
-  string16 GetSubjectNameFromDigitalSignature(const base::FilePath& filename);
+  base::string16 GetSubjectNameFromDigitalSignature(
+      const base::FilePath& filename);
 
   // The typedef for the vector that maps a regular file path to %env_var%.
-  typedef std::vector< std::pair<string16, string16> > PathMapping;
+  typedef std::vector< std::pair<string16, base::string16> > PathMapping;
 
   // The vector of paths to %env_var%, used to account for differences in
   // where people keep there files, c:\windows vs. d:\windows, etc.
diff --git a/chrome/browser/errorpage_browsertest.cc b/chrome/browser/errorpage_browsertest.cc
index aa90a22..9c83298 100644
--- a/chrome/browser/errorpage_browsertest.cc
+++ b/chrome/browser/errorpage_browsertest.cc
@@ -129,11 +129,11 @@ class TestFailProvisionalLoadObserver : public content::WebContentsObserver {
   // This method is invoked when the provisional load failed.
   virtual void DidFailProvisionalLoad(
       int64 frame_id,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& validated_url,
       int error_code,
-      const string16& error_description,
+      const base::string16& error_description,
       content::RenderViewHost* render_view_host) OVERRIDE {
     fail_url_ = validated_url;
   }
@@ -304,7 +304,7 @@ IN_PROC_BROWSER_TEST_F(ErrorPageTest, IFrameDNSError_JavaScript) {
         content::NOTIFICATION_LOAD_STOP,
         content::Source<NavigationController>(&wc->GetController()));
     wc->GetRenderViewHost()->ExecuteJavascriptInWebFrame(
-        string16(), ASCIIToUTF16(script));
+        base::string16(), ASCIIToUTF16(script));
     load_observer.Wait();
 
     // Ensure we saw the expected failure.
@@ -325,7 +325,7 @@ IN_PROC_BROWSER_TEST_F(ErrorPageTest, IFrameDNSError_JavaScript) {
         content::NOTIFICATION_LOAD_STOP,
         content::Source<NavigationController>(&wc->GetController()));
     wc->GetRenderViewHost()->ExecuteJavascriptInWebFrame(
-        string16(), ASCIIToUTF16(script));
+        base::string16(), ASCIIToUTF16(script));
     load_observer.Wait();
   }
 
@@ -337,7 +337,7 @@ IN_PROC_BROWSER_TEST_F(ErrorPageTest, IFrameDNSError_JavaScript) {
         content::NOTIFICATION_LOAD_STOP,
         content::Source<NavigationController>(&wc->GetController()));
     wc->GetRenderViewHost()->ExecuteJavascriptInWebFrame(
-        string16(), ASCIIToUTF16(script));
+        base::string16(), ASCIIToUTF16(script));
     load_observer.Wait();
 
     EXPECT_EQ(fail_url, fail_observer.fail_url());
diff --git a/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc b/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
index 446e84f..ccfed7e 100644
--- a/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
+++ b/chrome/browser/extensions/api/bookmarks/bookmarks_api.cc
@@ -532,7 +532,7 @@ bool BookmarksCreateFunction::RunImpl() {
     }
   }
 
-  string16 title;  // Optional.
+  base::string16 title;  // Optional.
   if (params->bookmark.title.get())
     title = UTF8ToUTF16(*params->bookmark.title.get());
 
@@ -648,7 +648,7 @@ bool BookmarksUpdateFunction::RunImpl() {
   EXTENSION_FUNCTION_VALIDATE(params.get());
 
   // Optional but we need to distinguish non present from an empty title.
-  string16 title;
+  base::string16 title;
   bool has_title = false;
   if (params->changes.title.get()) {
     title = UTF8ToUTF16(*params->changes.title);
@@ -930,7 +930,7 @@ void BookmarksIOFunction::ShowSelectFileDialog(
   // a case if file-selection dialogs are forbidden by policy, we will not
   // show an InfoBar, which is better than letting one appear out of the blue.
   select_file_dialog_->SelectFile(type,
-                                  string16(),
+                                  base::string16(),
                                   default_path,
                                   &file_type_info,
                                   0,
diff --git a/chrome/browser/extensions/api/commands/command_service.cc b/chrome/browser/extensions/api/commands/command_service.cc
index cfcf660..37f51b3 100644
--- a/chrome/browser/extensions/api/commands/command_service.cc
+++ b/chrome/browser/extensions/api/commands/command_service.cc
@@ -344,7 +344,7 @@ Command CommandService::FindCommandByName(
     CHECK(tokens.size() >= 2);
     shortcut = tokens[1];
 
-    return Command(command_name, string16(), shortcut, global);
+    return Command(command_name, base::string16(), shortcut, global);
   }
 
   return Command();
diff --git a/chrome/browser/extensions/api/commands/commands.cc b/chrome/browser/extensions/api/commands/commands.cc
index be1c95b..a4a837d 100644
--- a/chrome/browser/extensions/api/commands/commands.cc
+++ b/chrome/browser/extensions/api/commands/commands.cc
@@ -15,7 +15,7 @@ base::DictionaryValue* CreateCommandValue(
   result->SetString("description", command.description());
   result->SetString("shortcut",
                     active ? command.accelerator().GetShortcutText() :
-                             string16());
+                             base::string16());
   return result;
 }
 
diff --git a/chrome/browser/extensions/api/debugger/debugger_api.cc b/chrome/browser/extensions/api/debugger/debugger_api.cc
index b9bace4..da51f9e 100644
--- a/chrome/browser/extensions/api/debugger/debugger_api.cc
+++ b/chrome/browser/extensions/api/debugger/debugger_api.cc
@@ -159,7 +159,7 @@ class ExtensionDevToolsInfoBarDelegate : public ConfirmInfoBarDelegate {
   virtual Type GetInfoBarType() const OVERRIDE;
   virtual bool ShouldExpireInternal(
       const content::LoadCommittedDetails& details) const OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
   virtual int GetButtons() const OVERRIDE;
   virtual bool Cancel() OVERRIDE;
 
diff --git a/chrome/browser/extensions/api/declarative/declarative_apitest.cc b/chrome/browser/extensions/api/declarative/declarative_apitest.cc
index 40209a7..47356a1 100644
--- a/chrome/browser/extensions/api/declarative/declarative_apitest.cc
+++ b/chrome/browser/extensions/api/declarative/declarative_apitest.cc
@@ -102,7 +102,7 @@ const char kRedirectToDataNoRules[] =
 class DeclarativeApiTest : public ExtensionApiTest {
  public:
   std::string GetTitle() {
-    string16 title(
+    base::string16 title(
         browser()->tab_strip_model()->GetActiveWebContents()->GetTitle());
     return base::UTF16ToUTF8(title);
   }
diff --git a/chrome/browser/extensions/api/desktop_capture/desktop_capture_apitest.cc b/chrome/browser/extensions/api/desktop_capture/desktop_capture_apitest.cc
index 4bbe02b..b41b873 100644
--- a/chrome/browser/extensions/api/desktop_capture/desktop_capture_apitest.cc
+++ b/chrome/browser/extensions/api/desktop_capture/desktop_capture_apitest.cc
@@ -35,7 +35,7 @@ class FakeDesktopMediaPicker : public DesktopMediaPicker {
   // DesktopMediaPicker interface.
   virtual void Show(gfx::NativeWindow context,
                     gfx::NativeWindow parent,
-                    const string16& app_name,
+                    const base::string16& app_name,
                     scoped_ptr<DesktopMediaList> model,
                     const DoneCallback& done_callback) OVERRIDE {
     if (!expect_cancelled_) {
diff --git a/chrome/browser/extensions/api/developer_private/developer_private_api.cc b/chrome/browser/extensions/api/developer_private/developer_private_api.cc
index 79817f1..db64c33 100644
--- a/chrome/browser/extensions/api/developer_private/developer_private_api.cc
+++ b/chrome/browser/extensions/api/developer_private/developer_private_api.cc
@@ -818,7 +818,7 @@ bool DeveloperPrivateInspectFunction::RunImpl() {
 DeveloperPrivateInspectFunction::~DeveloperPrivateInspectFunction() {}
 
 bool DeveloperPrivateLoadUnpackedFunction::RunImpl() {
-  string16 select_title =
+  base::string16 select_title =
       l10n_util::GetStringUTF16(IDS_EXTENSION_LOAD_FROM_DIRECTORY);
 
   // Balanced in FileSelected / FileSelectionCanceled.
@@ -849,7 +849,7 @@ void DeveloperPrivateLoadUnpackedFunction::FileSelectionCanceled() {
 bool DeveloperPrivateChooseEntryFunction::ShowPicker(
     ui::SelectFileDialog::Type picker_type,
     const base::FilePath& last_directory,
-    const string16& select_title,
+    const base::string16& select_title,
     const ui::SelectFileDialog::FileTypeInfo& info,
     int file_type_index) {
   ShellWindowRegistry* registry = ShellWindowRegistry::Get(GetProfile());
@@ -1178,7 +1178,7 @@ bool DeveloperPrivateChoosePathFunction::RunImpl() {
   if (params->select_type == developer::SELECT_TYPE_FILE) {
     type = ui::SelectFileDialog::SELECT_OPEN_FILE;
   }
-  string16 select_title;
+  base::string16 select_title;
 
   int file_type_index = 0;
   if (params->file_type == developer::FILE_TYPE_LOAD)
diff --git a/chrome/browser/extensions/api/developer_private/developer_private_api.h b/chrome/browser/extensions/api/developer_private/developer_private_api.h
index 4af2eec..d747fd1 100644
--- a/chrome/browser/extensions/api/developer_private/developer_private_api.h
+++ b/chrome/browser/extensions/api/developer_private/developer_private_api.h
@@ -274,7 +274,7 @@ class DeveloperPrivateChooseEntryFunction : public ChromeAsyncExtensionFunction,
   virtual bool RunImpl() OVERRIDE;
   bool ShowPicker(ui::SelectFileDialog::Type picker_type,
                   const base::FilePath& last_directory,
-                  const string16& select_title,
+                  const base::string16& select_title,
                   const ui::SelectFileDialog::FileTypeInfo& info,
                   int file_type_index);
 
diff --git a/chrome/browser/extensions/api/developer_private/entry_picker.cc b/chrome/browser/extensions/api/developer_private/entry_picker.cc
index 91bc1f3..f21371c 100644
--- a/chrome/browser/extensions/api/developer_private/entry_picker.cc
+++ b/chrome/browser/extensions/api/developer_private/entry_picker.cc
@@ -29,7 +29,7 @@ EntryPicker::EntryPicker(EntryPickerClient* client,
                          content::WebContents* web_contents,
                          ui::SelectFileDialog::Type picker_type,
                          const base::FilePath& last_directory,
-                         const string16& select_title,
+                         const base::string16& select_title,
                          const ui::SelectFileDialog::FileTypeInfo& info,
                          int file_type_index)
     : client_(client) {
diff --git a/chrome/browser/extensions/api/developer_private/entry_picker.h b/chrome/browser/extensions/api/developer_private/entry_picker.h
index 592174a..69aedba 100644
--- a/chrome/browser/extensions/api/developer_private/entry_picker.h
+++ b/chrome/browser/extensions/api/developer_private/entry_picker.h
@@ -29,7 +29,7 @@ class EntryPicker : public ui::SelectFileDialog::Listener {
               content::WebContents* web_contents,
               ui::SelectFileDialog::Type picker_type,
               const base::FilePath& last_directory,
-              const string16& select_title,
+              const base::string16& select_title,
               const ui::SelectFileDialog::FileTypeInfo& info,
               int file_type_index);
 
diff --git a/chrome/browser/extensions/api/file_system/file_system_api.cc b/chrome/browser/extensions/api/file_system/file_system_api.cc
index 7dac9bb..67d717b 100644
--- a/chrome/browser/extensions/api/file_system/file_system_api.cc
+++ b/chrome/browser/extensions/api/file_system/file_system_api.cc
@@ -153,7 +153,7 @@ bool g_allow_directory_access_for_test = false;
 bool GetFileTypesFromAcceptOption(
     const file_system::AcceptOption& accept_option,
     std::vector<base::FilePath::StringType>* extensions,
-    string16* description) {
+    base::string16* description) {
   std::set<base::FilePath::StringType> extension_set;
   int description_id = 0;
 
@@ -469,7 +469,7 @@ class FileSystemChooseEntryFunction::FilePicker
     }
 
     select_file_dialog_->SelectFile(picker_type,
-                                    string16(),
+                                    base::string16(),
                                     suggested_name,
                                     &file_type_info,
                                     0,
@@ -774,7 +774,7 @@ void FileSystemChooseEntryFunction::BuildFileTypeInfo(
     typedef file_system::AcceptOption AcceptOption;
     for (std::vector<linked_ptr<AcceptOption> >::const_iterator iter =
             accepts->begin(); iter != accepts->end(); ++iter) {
-      string16 description;
+      base::string16 description;
       std::vector<base::FilePath::StringType> extensions;
 
       if (!GetFileTypesFromAcceptOption(**iter, &extensions, &description))
diff --git a/chrome/browser/extensions/api/history/history_api.cc b/chrome/browser/extensions/api/history/history_api.cc
index e55b726..1a46508 100644
--- a/chrome/browser/extensions/api/history/history_api.cc
+++ b/chrome/browser/extensions/api/history/history_api.cc
@@ -378,7 +378,7 @@ bool HistorySearchFunction::RunAsyncImpl() {
   scoped_ptr<Search::Params> params(Search::Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params.get());
 
-  string16 search_text = UTF8ToUTF16(params->query.text);
+  base::string16 search_text = UTF8ToUTF16(params->query.text);
 
   history::QueryOptions options;
   options.SetRecentDayRange(1);
diff --git a/chrome/browser/extensions/api/i18n/i18n_apitest.cc b/chrome/browser/extensions/api/i18n/i18n_apitest.cc
index f6f1ce8..93e3b54 100644
--- a/chrome/browser/extensions/api/i18n/i18n_apitest.cc
+++ b/chrome/browser/extensions/api/i18n/i18n_apitest.cc
@@ -46,7 +46,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, I18NUpdate) {
       embedded_test_server()->GetURL("/extensions/test_file.html"));
   EXPECT_TRUE(catcher.GetNextResult());
 
-  string16 title;
+  base::string16 title;
   ui_test_utils::GetCurrentTabTitle(browser(), &title);
   EXPECT_EQ(std::string("FIRSTMESSAGE"), UTF16ToUTF8(title));
 
diff --git a/chrome/browser/extensions/api/identity/web_auth_flow.cc b/chrome/browser/extensions/api/identity/web_auth_flow.cc
index eb61068..0ade81b 100644
--- a/chrome/browser/extensions/api/identity/web_auth_flow.cc
+++ b/chrome/browser/extensions/api/identity/web_auth_flow.cc
@@ -222,13 +222,14 @@ void WebAuthFlow::DidStartProvisionalLoadForFrame(
     BeforeUrlLoaded(validated_url);
 }
 
-void WebAuthFlow::DidFailProvisionalLoad(int64 frame_id,
-                                         const string16& frame_unique_name,
-                                         bool is_main_frame,
-                                         const GURL& validated_url,
-                                         int error_code,
-                                         const string16& error_description,
-                                         RenderViewHost* render_view_host) {
+void WebAuthFlow::DidFailProvisionalLoad(
+    int64 frame_id,
+    const base::string16& frame_unique_name,
+    bool is_main_frame,
+    const GURL& validated_url,
+    int error_code,
+    const base::string16& error_description,
+    RenderViewHost* render_view_host) {
   if (delegate_)
     delegate_->OnAuthFlowFailure(LOAD_FAILED);
 }
diff --git a/chrome/browser/extensions/api/identity/web_auth_flow.h b/chrome/browser/extensions/api/identity/web_auth_flow.h
index d9a4336..ed96cfa 100644
--- a/chrome/browser/extensions/api/identity/web_auth_flow.h
+++ b/chrome/browser/extensions/api/identity/web_auth_flow.h
@@ -118,11 +118,11 @@ class WebAuthFlow : public content::NotificationObserver,
       bool is_iframe_srcdoc,
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void DidFailProvisionalLoad(int64 frame_id,
-                                      const string16& frame_unique_name,
+                                      const base::string16& frame_unique_name,
                                       bool is_main_frame,
                                       const GURL& validated_url,
                                       int error_code,
-                                      const string16& error_description,
+                                      const base::string16& error_description,
                                       content::RenderViewHost* render_view_host)
       OVERRIDE;
 
diff --git a/chrome/browser/extensions/api/input/input.cc b/chrome/browser/extensions/api/input/input.cc
index e8ec9a8..35b5f9d 100644
--- a/chrome/browser/extensions/api/input/input.cc
+++ b/chrome/browser/extensions/api/input/input.cc
@@ -34,7 +34,7 @@ bool VirtualKeyboardPrivateInsertTextFunction::RunImpl() {
 #if defined(USE_ASH)
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
-  string16 text;
+  base::string16 text;
   EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &text));
 
   return keyboard::InsertText(text, ash::Shell::GetPrimaryRootWindow());
diff --git a/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_apitest.cc b/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_apitest.cc
index f39ccdc..447fcda 100644
--- a/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_apitest.cc
+++ b/chrome/browser/extensions/api/media_galleries_private/media_galleries_private_apitest.cc
@@ -89,7 +89,7 @@ class MediaGalleriesPrivateApiTest : public ExtensionApiTest {
   void Attach() {
     DCHECK(StorageMonitor::GetInstance()->IsInitialized());
     StorageInfo info(device_id_, ASCIIToUTF16(kDeviceName), kDevicePath,
-                     string16(), string16(), string16(), 0);
+                     base::string16(), base::string16(), base::string16(), 0);
     StorageMonitor::GetInstance()->receiver()->ProcessAttach(info);
     content::RunAllPendingInMessageLoop();
   }
diff --git a/chrome/browser/extensions/api/messaging/incognito_connectability.cc b/chrome/browser/extensions/api/messaging/incognito_connectability.cc
index d9f41c6..09a8f05 100644
--- a/chrome/browser/extensions/api/messaging/incognito_connectability.cc
+++ b/chrome/browser/extensions/api/messaging/incognito_connectability.cc
@@ -79,7 +79,7 @@ bool IncognitoConnectability::Query(const Extension* extension,
       result = chrome::ShowMessageBox(
           web_contents ? web_contents->GetView()->GetTopLevelNativeWindow()
                        : NULL,
-          string16(),  // no title
+          base::string16(),  // no title
           l10n_util::GetStringFUTF16(template_id,
                                      UTF8ToUTF16(origin.spec()),
                                      UTF8ToUTF16(extension->name())),
diff --git a/chrome/browser/extensions/api/messaging/native_message_process_host_unittest.cc b/chrome/browser/extensions/api/messaging/native_message_process_host_unittest.cc
index b3b09f5..a2e7d18 100644
--- a/chrome/browser/extensions/api/messaging/native_message_process_host_unittest.cc
+++ b/chrome/browser/extensions/api/messaging/native_message_process_host_unittest.cc
@@ -203,7 +203,7 @@ TEST_F(NativeMessagingTest, SingleSendMessageWrite) {
 
   base::PlatformFile read_file;
 #if defined(OS_WIN)
-  string16 pipe_name = base::StringPrintf(
+  base::string16 pipe_name = base::StringPrintf(
       L"\\\\.\\pipe\\chrome.nativeMessaging.out.%llx", base::RandUint64());
   base::win::ScopedHandle write_handle(
       CreateNamedPipeW(pipe_name.c_str(),
diff --git a/chrome/browser/extensions/api/messaging/native_process_launcher_win.cc b/chrome/browser/extensions/api/messaging/native_process_launcher_win.cc
index 31fbdc8..36a0653 100644
--- a/chrome/browser/extensions/api/messaging/native_process_launcher_win.cc
+++ b/chrome/browser/extensions/api/messaging/native_process_launcher_win.cc
@@ -27,16 +27,16 @@ namespace {
 
 // Reads path to the native messaging host manifest from the registry. Returns
 // empty string if the path isn't found.
-string16 GetManifestPath(const string16& native_host_name, DWORD flags) {
+string16 GetManifestPath(const base::string16& native_host_name, DWORD flags) {
   base::win::RegKey key;
-  string16 result;
+  base::string16 result;
 
   if (key.Open(HKEY_LOCAL_MACHINE, kNativeMessagingRegistryKey,
                KEY_QUERY_VALUE | flags) != ERROR_SUCCESS ||
       key.OpenKey(native_host_name.c_str(),
                   KEY_QUERY_VALUE | flags) != ERROR_SUCCESS ||
       key.ReadValue(NULL, &result) != ERROR_SUCCESS) {
-    return string16();
+    return base::string16();
   }
 
   return result;
@@ -48,10 +48,10 @@ string16 GetManifestPath(const string16& native_host_name, DWORD flags) {
 base::FilePath NativeProcessLauncher::FindManifest(
     const std::string& native_host_name,
     std::string* error_message) {
-  string16 native_host_name_wide = UTF8ToUTF16(native_host_name);
+  base::string16 native_host_name_wide = UTF8ToUTF16(native_host_name);
 
   // First check 32-bit registry and then try 64-bit.
-  string16 manifest_path_str =
+  base::string16 manifest_path_str =
       GetManifestPath(native_host_name_wide, KEY_WOW64_32KEY);
   if (manifest_path_str.empty())
     manifest_path_str = GetManifestPath(native_host_name_wide, KEY_WOW64_64KEY);
@@ -91,9 +91,9 @@ bool NativeProcessLauncher::LaunchNativeProcess(
 
   uint64 pipe_name_token;
   crypto::RandBytes(&pipe_name_token, sizeof(pipe_name_token));
-  string16 out_pipe_name = base::StringPrintf(
+  base::string16 out_pipe_name = base::StringPrintf(
       L"\\\\.\\pipe\\chrome.nativeMessaging.out.%llx", pipe_name_token);
-  string16 in_pipe_name = base::StringPrintf(
+  base::string16 in_pipe_name = base::StringPrintf(
       L"\\\\.\\pipe\\chrome.nativeMessaging.in.%llx", pipe_name_token);
 
   // Create the pipes to read and write from.
@@ -127,9 +127,9 @@ bool NativeProcessLauncher::LaunchNativeProcess(
   scoped_ptr<wchar_t[]> comspec(new wchar_t[comspec_length]);
   ::GetEnvironmentVariable(L"COMSPEC", comspec.get(), comspec_length);
 
-  string16 command_line_string = command_line.GetCommandLineString();
+  base::string16 command_line_string = command_line.GetCommandLineString();
 
-  string16 command = base::StringPrintf(
+  base::string16 command = base::StringPrintf(
       L"%ls /c %ls < %ls > %ls",
       comspec.get(), command_line_string.c_str(),
       in_pipe_name.c_str(), out_pipe_name.c_str());
diff --git a/chrome/browser/extensions/api/notifications/notifications_api.cc b/chrome/browser/extensions/api/notifications/notifications_api.cc
index 79fb5c7..27c862e 100644
--- a/chrome/browser/extensions/api/notifications/notifications_api.cc
+++ b/chrome/browser/extensions/api/notifications/notifications_api.cc
@@ -249,8 +249,8 @@ bool NotificationsApiFunction::CreateNotification(
   // Extract required fields: type, title, message, and icon.
   message_center::NotificationType type =
       MapApiTemplateTypeToType(options->type);
-  const string16 title(UTF8ToUTF16(*options->title));
-  const string16 message(UTF8ToUTF16(*options->message));
+  const base::string16 title(UTF8ToUTF16(*options->title));
+  const base::string16 message(UTF8ToUTF16(*options->message));
   gfx::Image icon;
 
   // TODO(dewittj): Return error if this fails.
diff --git a/chrome/browser/extensions/api/notifications/notifications_apitest.cc b/chrome/browser/extensions/api/notifications/notifications_apitest.cc
index aa26396..59d597f 100644
--- a/chrome/browser/extensions/api/notifications/notifications_apitest.cc
+++ b/chrome/browser/extensions/api/notifications/notifications_apitest.cc
@@ -769,7 +769,7 @@ IN_PROC_BROWSER_TEST_F(NotificationsApiTest, MAYBE_TestGetPermissionLevel) {
     message_center::NotifierId notifier_id(
         message_center::NotifierId::APPLICATION,
         empty_extension->id());
-    message_center::Notifier notifier(notifier_id, string16(), true);
+    message_center::Notifier notifier(notifier_id, base::string16(), true);
     g_browser_process->message_center()->GetNotifierSettingsProvider()->
         SetNotifierEnabled(notifier, false);
 
@@ -806,7 +806,7 @@ IN_PROC_BROWSER_TEST_F(NotificationsApiTest,
     message_center::NotifierId notifier_id(
         message_center::NotifierId::APPLICATION,
         extension->id());
-    message_center::Notifier notifier(notifier_id, string16(), true);
+    message_center::Notifier notifier(notifier_id, base::string16(), true);
     g_browser_process->message_center()->GetNotifierSettingsProvider()->
         SetNotifierEnabled(notifier, false);
 
@@ -820,7 +820,7 @@ IN_PROC_BROWSER_TEST_F(NotificationsApiTest,
     message_center::NotifierId notifier_id(
         message_center::NotifierId::APPLICATION,
         extension->id());
-    message_center::Notifier notifier(notifier_id, string16(), false);
+    message_center::Notifier notifier(notifier_id, base::string16(), false);
     g_browser_process->message_center()->GetNotifierSettingsProvider()->
         SetNotifierEnabled(notifier, true);
 
diff --git a/chrome/browser/extensions/api/omnibox/omnibox_api.cc b/chrome/browser/extensions/api/omnibox/omnibox_api.cc
index 85df2cf..f1d7421 100644
--- a/chrome/browser/extensions/api/omnibox/omnibox_api.cc
+++ b/chrome/browser/extensions/api/omnibox/omnibox_api.cc
@@ -317,7 +317,7 @@ ACMatchClassifications StyleTypesToACMatchClassifications(
     const omnibox::SuggestResult &suggestion) {
   ACMatchClassifications match_classifications;
   if (suggestion.description_styles) {
-    string16 description = UTF8ToUTF16(suggestion.description);
+    base::string16 description = UTF8ToUTF16(suggestion.description);
     std::vector<int> styles(description.length(), 0);
 
     for (std::vector<linked_ptr<omnibox::SuggestResult::DescriptionStylesType> >
@@ -368,7 +368,7 @@ ACMatchClassifications StyleTypesToACMatchClassifications(
 void ApplyDefaultSuggestionForExtensionKeyword(
     Profile* profile,
     const TemplateURL* keyword,
-    const string16& remaining_input,
+    const base::string16& remaining_input,
     AutocompleteMatch* match) {
   DCHECK(keyword->GetType() == TemplateURL::OMNIBOX_API_EXTENSION);
 
@@ -377,18 +377,18 @@ void ApplyDefaultSuggestionForExtensionKeyword(
   if (!suggestion || suggestion->description.empty())
     return;  // fall back to the universal default
 
-  const string16 kPlaceholderText(ASCIIToUTF16("%s"));
-  const string16 kReplacementText(ASCIIToUTF16("<input>"));
+  const base::string16 kPlaceholderText(ASCIIToUTF16("%s"));
+  const base::string16 kReplacementText(ASCIIToUTF16("<input>"));
 
-  string16 description = UTF8ToUTF16(suggestion->description);
+  base::string16 description = UTF8ToUTF16(suggestion->description);
   ACMatchClassifications& description_styles = match->contents_class;
   description_styles = StyleTypesToACMatchClassifications(*suggestion);
 
   // Replace "%s" with the user's input and adjust the style offsets to the
   // new length of the description.
   size_t placeholder(description.find(kPlaceholderText, 0));
-  if (placeholder != string16::npos) {
-    string16 replacement =
+  if (placeholder != base::string16::npos) {
+    base::string16 replacement =
         remaining_input.empty() ? kReplacementText : remaining_input;
     description.replace(placeholder, kPlaceholderText.length(), replacement);
 
diff --git a/chrome/browser/extensions/api/omnibox/omnibox_api.h b/chrome/browser/extensions/api/omnibox/omnibox_api.h
index f5a7de7..500da78 100644
--- a/chrome/browser/extensions/api/omnibox/omnibox_api.h
+++ b/chrome/browser/extensions/api/omnibox/omnibox_api.h
@@ -161,7 +161,7 @@ class OmniboxSetDefaultSuggestionFunction : public ChromeSyncExtensionFunction {
 void ApplyDefaultSuggestionForExtensionKeyword(
     Profile* profile,
     const TemplateURL* keyword,
-    const string16& remaining_input,
+    const base::string16& remaining_input,
     AutocompleteMatch* match);
 
 // This function converts style information populated by the JSON schema
diff --git a/chrome/browser/extensions/api/omnibox/omnibox_api_browsertest.cc b/chrome/browser/extensions/api/omnibox/omnibox_api_browsertest.cc
index 42640ad..ef2b413 100644
--- a/chrome/browser/extensions/api/omnibox/omnibox_api_browsertest.cc
+++ b/chrome/browser/extensions/api/omnibox/omnibox_api_browsertest.cc
@@ -32,9 +32,9 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, Basic) {
   // it.
   {
     autocomplete_controller->Start(
-        AutocompleteInput(ASCIIToUTF16("keywor"), string16::npos, string16(),
-                          GURL(), AutocompleteInput::NTP, true, false,
-                          true, AutocompleteInput::ALL_MATCHES));
+        AutocompleteInput(ASCIIToUTF16("keywor"), base::string16::npos,
+                          base::string16(), GURL(), AutocompleteInput::NTP,
+                          true, false, true, AutocompleteInput::ALL_MATCHES));
     WaitForAutocompleteDone(autocomplete_controller);
     EXPECT_TRUE(autocomplete_controller->done());
 
@@ -54,9 +54,10 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, Basic) {
   // Test that our extension can send suggestions back to us.
   {
     autocomplete_controller->Start(
-        AutocompleteInput(ASCIIToUTF16("keyword suggestio"), string16::npos,
-                          string16(), GURL(), AutocompleteInput::NTP,
-                          true, false, true, AutocompleteInput::ALL_MATCHES));
+        AutocompleteInput(ASCIIToUTF16("keyword suggestio"),
+                          base::string16::npos, base::string16(), GURL(),
+                          AutocompleteInput::NTP, true, false, true,
+                          AutocompleteInput::ALL_MATCHES));
     WaitForAutocompleteDone(autocomplete_controller);
     EXPECT_TRUE(autocomplete_controller->done());
 
@@ -90,7 +91,7 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, Basic) {
     EXPECT_EQ(AutocompleteProvider::TYPE_KEYWORD,
               result.match_at(3).provider->type());
 
-    string16 description =
+    base::string16 description =
         ASCIIToUTF16("Description with style: <match>, [dim], (url till end)");
     EXPECT_EQ(description, result.match_at(1).contents);
     ASSERT_EQ(6u, result.match_at(1).contents_class.size());
@@ -164,8 +165,8 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, OnInputEntered) {
   omnibox_view->OnAfterPossibleChange();
 
   autocomplete_controller->Start(
-      AutocompleteInput(ASCIIToUTF16("keyword command"), string16::npos,
-                        string16(), GURL(), AutocompleteInput::NTP,
+      AutocompleteInput(ASCIIToUTF16("keyword command"), base::string16::npos,
+                        base::string16(), GURL(), AutocompleteInput::NTP,
                         true, false, true, AutocompleteInput::ALL_MATCHES));
   omnibox_view->model()->AcceptInput(CURRENT_TAB, false);
   WaitForAutocompleteDone(autocomplete_controller);
@@ -179,8 +180,8 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, OnInputEntered) {
   EXPECT_TRUE(autocomplete_controller->done());
 
   autocomplete_controller->Start(
-      AutocompleteInput(ASCIIToUTF16("keyword newtab"), string16::npos,
-                        string16(), GURL(), AutocompleteInput::NTP,
+      AutocompleteInput(ASCIIToUTF16("keyword newtab"), base::string16::npos,
+                        base::string16(), GURL(), AutocompleteInput::NTP,
                         true, false, true, AutocompleteInput::ALL_MATCHES));
   omnibox_view->model()->AcceptInput(NEW_FOREGROUND_TAB, false);
   WaitForAutocompleteDone(autocomplete_controller);
@@ -216,9 +217,10 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, DISABLED_IncognitoSplitMode) {
   // Test that we get the incognito-specific suggestions.
   {
     autocomplete_controller->Start(
-        AutocompleteInput(ASCIIToUTF16("keyword suggestio"), string16::npos,
-                          string16(), GURL(), AutocompleteInput::NTP,
-                          true, false, true, AutocompleteInput::ALL_MATCHES));
+        AutocompleteInput(ASCIIToUTF16("keyword suggestio"),
+                          base::string16::npos, base::string16(), GURL(),
+                          AutocompleteInput::NTP, true, false, true,
+                          AutocompleteInput::ALL_MATCHES));
     WaitForAutocompleteDone(autocomplete_controller);
     EXPECT_TRUE(autocomplete_controller->done());
 
@@ -239,7 +241,7 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, DISABLED_IncognitoSplitMode) {
     ResultCatcher catcher;
     autocomplete_controller->Start(
         AutocompleteInput(ASCIIToUTF16("keyword command incognito"),
-                          string16::npos, string16(), GURL(),
+                          base::string16::npos, base::string16(), GURL(),
                           AutocompleteInput::NTP, true, false, true,
                           AutocompleteInput::ALL_MATCHES));
     location_bar->AcceptInput();
diff --git a/chrome/browser/extensions/api/omnibox/omnibox_api_interactive_test.cc b/chrome/browser/extensions/api/omnibox/omnibox_api_interactive_test.cc
index 232b580..d8b68c2 100644
--- a/chrome/browser/extensions/api/omnibox/omnibox_api_interactive_test.cc
+++ b/chrome/browser/extensions/api/omnibox/omnibox_api_interactive_test.cc
@@ -41,8 +41,8 @@ IN_PROC_BROWSER_TEST_F(OmniboxApiTest, PopupStaysClosed) {
   // directly, figure out how to send it via the proper calls to
   // location_bar or location_bar->().
   autocomplete_controller->Start(
-      AutocompleteInput(ASCIIToUTF16("keyword command"), string16::npos,
-                        string16(), GURL(), AutocompleteInput::NTP,
+      AutocompleteInput(ASCIIToUTF16("keyword command"), base::string16::npos,
+                        base::string16(), GURL(), AutocompleteInput::NTP,
                         true, false, true, AutocompleteInput::ALL_MATCHES));
   location_bar->AcceptInput();
   WaitForAutocompleteDone(autocomplete_controller);
diff --git a/chrome/browser/extensions/api/omnibox/omnibox_api_testbase.h b/chrome/browser/extensions/api/omnibox/omnibox_api_testbase.h
index c14e521..169ca90 100644
--- a/chrome/browser/extensions/api/omnibox/omnibox_api_testbase.h
+++ b/chrome/browser/extensions/api/omnibox/omnibox_api_testbase.h
@@ -43,7 +43,8 @@ class OmniboxApiTest : public ExtensionApiTest {
     }
   }
 
-  static string16 AutocompleteResultAsString(const AutocompleteResult& result) {
+  static base::string16 AutocompleteResultAsString(
+      const AutocompleteResult& result) {
     std::string output(base::StringPrintf("{%" PRIuS "} ", result.size()));
     for (size_t i = 0; i < result.size(); ++i) {
       AutocompleteMatch match = result.match_at(i);
diff --git a/chrome/browser/extensions/api/proxy/proxy_api.cc b/chrome/browser/extensions/api/proxy/proxy_api.cc
index a115a1b..d5b60c9 100644
--- a/chrome/browser/extensions/api/proxy/proxy_api.cc
+++ b/chrome/browser/extensions/api/proxy/proxy_api.cc
@@ -57,7 +57,7 @@ void ProxyEventRouter::OnPACScriptError(
     EventRouterForwarder* event_router,
     void* profile,
     int line_number,
-    const string16& error) {
+    const base::string16& error) {
   scoped_ptr<base::ListValue> args(new base::ListValue());
   base::DictionaryValue* dict = new base::DictionaryValue();
   dict->SetBoolean(keys::kProxyEventFatal, false);
diff --git a/chrome/browser/extensions/api/proxy/proxy_api.h b/chrome/browser/extensions/api/proxy/proxy_api.h
index 187d774..6d35047 100644
--- a/chrome/browser/extensions/api/proxy/proxy_api.h
+++ b/chrome/browser/extensions/api/proxy/proxy_api.h
@@ -55,7 +55,7 @@ class ProxyEventRouter {
   void OnPACScriptError(EventRouterForwarder* event_router,
                         void* profile,
                         int line_number,
-                        const string16& error);
+                        const base::string16& error);
 
  private:
   friend struct DefaultSingletonTraits<ProxyEventRouter>;
diff --git a/chrome/browser/extensions/api/proxy/proxy_api_helpers.cc b/chrome/browser/extensions/api/proxy/proxy_api_helpers.cc
index 1c0d693..fa88fbd 100644
--- a/chrome/browser/extensions/api/proxy/proxy_api_helpers.cc
+++ b/chrome/browser/extensions/api/proxy/proxy_api_helpers.cc
@@ -106,7 +106,7 @@ bool GetPacUrlFromExtensionPref(const base::DictionaryValue* proxy_config,
     return true;
 
   // TODO(battre): Handle UTF-8 URLs (http://crbug.com/72692).
-  string16 pac_url16;
+  base::string16 pac_url16;
   if (pac_dict->HasKey(keys::kProxyConfigPacScriptUrl) &&
       !pac_dict->GetString(keys::kProxyConfigPacScriptUrl, &pac_url16)) {
     LOG(ERROR) << "'pacScript.url' could not be parsed.";
@@ -131,7 +131,7 @@ bool GetPacDataFromExtensionPref(const base::DictionaryValue* proxy_config,
   if (!pac_dict)
     return true;
 
-  string16 pac_data16;
+  base::string16 pac_data16;
   if (pac_dict->HasKey(keys::kProxyConfigPacScriptData) &&
       !pac_dict->GetString(keys::kProxyConfigPacScriptData, &pac_data16)) {
     LOG(ERROR) << "'pacScript.data' could not be parsed.";
@@ -164,7 +164,7 @@ bool GetProxyServer(const base::DictionaryValue* proxy_server,
     scheme = default_scheme;
 
   // TODO(battre): handle UTF-8 in hostnames (http://crbug.com/72692).
-  string16 host16;
+  base::string16 host16;
   if (!proxy_server->GetString(keys::kProxyConfigRuleHost, &host16)) {
     LOG(ERROR) << "Could not parse a 'rules.*.host' entry.";
     *bad_message = true;
@@ -267,7 +267,7 @@ bool JoinUrlList(const base::ListValue* list,
       result.append(joiner);
 
     // TODO(battre): handle UTF-8 (http://crbug.com/72692).
-    string16 entry;
+    base::string16 entry;
     if (!list->GetString(i, &entry)) {
       LOG(ERROR) << "'rules.bypassList' could not be parsed.";
       *bad_message = true;
diff --git a/chrome/browser/extensions/api/push_messaging/push_messaging_canary_test.cc b/chrome/browser/extensions/api/push_messaging/push_messaging_canary_test.cc
index 077e79f..0902bad 100644
--- a/chrome/browser/extensions/api/push_messaging/push_messaging_canary_test.cc
+++ b/chrome/browser/extensions/api/push_messaging/push_messaging_canary_test.cc
@@ -156,7 +156,7 @@ IN_PROC_BROWSER_TEST_F(PushMessagingCanaryTest, MANUAL_ReceivesPush) {
   const std::string& client_secret = sync_setup_helper()->client_secret();
   const std::string& refresh_token = sync_setup_helper()->refresh_token();
 
-  const string16& script_string = UTF8ToUTF16(base::StringPrintf(
+  const base::string16& script_string = UTF8ToUTF16(base::StringPrintf(
       "startTestWithCredentials('%s', '%s', '%s');",
       client_id.c_str(), client_secret.c_str(), refresh_token.c_str()));
 
diff --git a/chrome/browser/extensions/api/serial/serial_port_enumerator_win.cc b/chrome/browser/extensions/api/serial/serial_port_enumerator_win.cc
index f3fac2f..213ef43 100644
--- a/chrome/browser/extensions/api/serial/serial_port_enumerator_win.cc
+++ b/chrome/browser/extensions/api/serial/serial_port_enumerator_win.cc
@@ -21,7 +21,7 @@ SerialPortEnumerator::GenerateValidSerialPortNames() {
       L"HARDWARE\\DEVICEMAP\\SERIALCOMM\\");
 
   for (; iter_key.Valid(); ++iter_key) {
-    string16 str(iter_key.Value());
+    base::string16 str(iter_key.Value());
     std::string device_string(WideToASCII(str));
     name_set.insert(device_string);
   }
diff --git a/chrome/browser/extensions/api/system_indicator/system_indicator_manager.cc b/chrome/browser/extensions/api/system_indicator/system_indicator_manager.cc
index f6bdc3e..fc6e8b0 100644
--- a/chrome/browser/extensions/api/system_indicator/system_indicator_manager.cc
+++ b/chrome/browser/extensions/api/system_indicator/system_indicator_manager.cc
@@ -112,7 +112,7 @@ ExtensionIndicatorIcon::ExtensionIndicatorIcon(const Extension* extension,
   // used as the tool tip.
   gfx::ImageSkia icon_image =
       icon_factory_.GetIcon(ExtensionAction::kDefaultTabId).AsImageSkia();
-  string16 tool_tip = UTF8ToUTF16(extension_->name());
+  base::string16 tool_tip = UTF8ToUTF16(extension_->name());
 
   icon_ = status_tray_->CreateStatusIcon(
       StatusTray::OTHER_ICON, icon_image, tool_tip);
diff --git a/chrome/browser/extensions/api/system_storage/storage_api_test_util.cc b/chrome/browser/extensions/api/system_storage/storage_api_test_util.cc
index 3a66314..930efb3 100644
--- a/chrome/browser/extensions/api/system_storage/storage_api_test_util.cc
+++ b/chrome/browser/extensions/api/system_storage/storage_api_test_util.cc
@@ -19,9 +19,9 @@ StorageInfo BuildStorageInfoFromTestStorageUnitInfo(
       unit.device_id,
       UTF8ToUTF16(unit.name),
       base::FilePath::StringType(), /* no location */
-      string16(), /* no storage label */
-      string16(), /* no storage vendor */
-      string16(), /* no storage model */
+      base::string16(), /* no storage label */
+      base::string16(), /* no storage vendor */
+      base::string16(), /* no storage model */
       unit.capacity);
 }
 
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
index 839b4b6..b9575dd 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
@@ -406,7 +406,7 @@ void WebNavigationTabObserver::DidStartProvisionalLoadForFrame(
 
 void WebNavigationTabObserver::DidCommitProvisionalLoadForFrame(
     int64 frame_num,
-    const string16& frame_unique_name,
+    const base::string16& frame_unique_name,
     bool is_main_frame,
     const GURL& url,
     content::PageTransition transition_type,
@@ -484,11 +484,11 @@ void WebNavigationTabObserver::DidCommitProvisionalLoadForFrame(
 
 void WebNavigationTabObserver::DidFailProvisionalLoad(
     int64 frame_num,
-    const string16& frame_unique_id,
+    const base::string16& frame_unique_id,
     bool is_main_frame,
     const GURL& validated_url,
     int error_code,
-    const string16& error_description,
+    const base::string16& error_description,
     content::RenderViewHost* render_view_host) {
   DVLOG(2) << "DidFailProvisionalLoad("
            << "render_view_host=" << render_view_host
@@ -592,7 +592,7 @@ void WebNavigationTabObserver::DidFailLoad(
     const GURL& validated_url,
     bool is_main_frame,
     int error_code,
-    const string16& error_description,
+    const base::string16& error_description,
     content::RenderViewHost* render_view_host) {
   DVLOG(2) << "DidFailLoad("
            << "render_view_host=" << render_view_host
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_api.h b/chrome/browser/extensions/api/web_navigation/web_navigation_api.h
index 1f3e357..c0dd107 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_api.h
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_api.h
@@ -66,18 +66,18 @@ class WebNavigationTabObserver
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void DidCommitProvisionalLoadForFrame(
       int64 frame_num,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& url,
       content::PageTransition transition_type,
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void DidFailProvisionalLoad(
       int64 frame_num,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& validated_url,
       int error_code,
-      const string16& error_description,
+      const base::string16& error_description,
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void DocumentLoadedInFrame(
       int64 frame_num,
@@ -92,7 +92,7 @@ class WebNavigationTabObserver
       const GURL& validated_url,
       bool is_main_frame,
       int error_code,
-      const string16& error_description,
+      const base::string16& error_description,
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void DidOpenRequestedURL(content::WebContents* new_contents,
                                    const GURL& url,
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
index 321a90b..5857139 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc
@@ -206,7 +206,7 @@ class DelayLoadStartAndExecuteJavascript
 
   virtual void DidCommitProvisionalLoadForFrame(
       int64 frame_id,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& url,
       content::PageTransition transition_type,
diff --git a/chrome/browser/extensions/api/web_request/web_request_api.cc b/chrome/browser/extensions/api/web_request/web_request_api.cc
index 008b6fc..e104f92 100644
--- a/chrome/browser/extensions/api/web_request/web_request_api.cc
+++ b/chrome/browser/extensions/api/web_request/web_request_api.cc
@@ -2301,8 +2301,8 @@ bool WebRequestEventHandled::RunImpl() {
       EXTENSION_FUNCTION_VALIDATE(value->GetDictionary(
           keys::kAuthCredentialsKey,
           &credentials_value));
-      string16 username;
-      string16 password;
+      base::string16 username;
+      base::string16 password;
       EXTENSION_FUNCTION_VALIDATE(
           credentials_value->GetString(keys::kUsernameKey, &username));
       EXTENSION_FUNCTION_VALIDATE(
diff --git a/chrome/browser/extensions/api/web_request/web_request_api_unittest.cc b/chrome/browser/extensions/api/web_request/web_request_api_unittest.cc
index d7a8bca..d5dfb49 100644
--- a/chrome/browser/extensions/api/web_request/web_request_api_unittest.cc
+++ b/chrome/browser/extensions/api/web_request/web_request_api_unittest.cc
@@ -1295,8 +1295,8 @@ TEST(ExtensionWebRequestHelpersTest, TestCalculateOnHeadersReceivedDelta) {
 TEST(ExtensionWebRequestHelpersTest, TestCalculateOnAuthRequiredDelta) {
   const bool cancel = true;
 
-  string16 username = ASCIIToUTF16("foo");
-  string16 password = ASCIIToUTF16("bar");
+  base::string16 username = ASCIIToUTF16("foo");
+  base::string16 password = ASCIIToUTF16("bar");
   scoped_ptr<net::AuthCredentials> credentials(
       new net::AuthCredentials(username, password));
 
@@ -2068,9 +2068,9 @@ TEST(ExtensionWebRequestHelpersTest, TestMergeOnAuthRequiredResponses) {
   net::BoundNetLog net_log = capturing_net_log.bound();
   ExtensionWarningSet warning_set;
   EventResponseDeltas deltas;
-  string16 username = ASCIIToUTF16("foo");
-  string16 password = ASCIIToUTF16("bar");
-  string16 password2 = ASCIIToUTF16("baz");
+  base::string16 username = ASCIIToUTF16("foo");
+  base::string16 password = ASCIIToUTF16("bar");
+  base::string16 password2 = ASCIIToUTF16("baz");
 
   // Check that we can handle if not returning credentials.
   linked_ptr<EventResponseDelta> d0(
diff --git a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
index 760072d..e3f7c7e 100644
--- a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
+++ b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
@@ -373,7 +373,7 @@ IN_PROC_BROWSER_TEST_F(HangoutServicesBrowserTest,
 
   content::TitleWatcher title_watcher(tab, ASCIIToUTF16("success"));
   title_watcher.AlsoWaitForTitle(ASCIIToUTF16("failure"));
-  string16 result = title_watcher.WaitAndGetTitle();
+  base::string16 result = title_watcher.WaitAndGetTitle();
   EXPECT_EQ(ASCIIToUTF16("success"), result);
 }
 
diff --git a/chrome/browser/extensions/api/webstore_private/webstore_private_apitest.cc b/chrome/browser/extensions/api/webstore_private/webstore_private_apitest.cc
index 1b3f2ab..4110415 100644
--- a/chrome/browser/extensions/api/webstore_private/webstore_private_apitest.cc
+++ b/chrome/browser/extensions/api/webstore_private/webstore_private_apitest.cc
@@ -151,14 +151,14 @@ IN_PROC_BROWSER_TEST_F(ExtensionWebstorePrivateApiTest,
                        DISABLED_FrameWebstorePageBlocked) {
   content::WebContents* contents =
       browser()->tab_strip_model()->GetActiveWebContents();
-  string16 expected_title = UTF8ToUTF16("PASS: about:blank");
-  string16 failure_title = UTF8ToUTF16("FAIL");
+  base::string16 expected_title = UTF8ToUTF16("PASS: about:blank");
+  base::string16 failure_title = UTF8ToUTF16("FAIL");
   content::TitleWatcher watcher(contents, expected_title);
   watcher.AlsoWaitForTitle(failure_title);
   GURL url = test_server()->GetURL(
       "files/extensions/api_test/webstore_private/noframe.html");
   ui_test_utils::NavigateToURL(browser(), url);
-  string16 final_title = watcher.WaitAndGetTitle();
+  base::string16 final_title = watcher.WaitAndGetTitle();
   EXPECT_EQ(expected_title, final_title);
 }
 
@@ -168,14 +168,14 @@ IN_PROC_BROWSER_TEST_F(ExtensionWebstorePrivateApiTest,
                        DISABLED_FrameErrorPageBlocked) {
   content::WebContents* contents =
       browser()->tab_strip_model()->GetActiveWebContents();
-  string16 expected_title = UTF8ToUTF16("PASS: about:blank");
-  string16 failure_title = UTF8ToUTF16("FAIL");
+  base::string16 expected_title = UTF8ToUTF16("PASS: about:blank");
+  base::string16 failure_title = UTF8ToUTF16("FAIL");
   content::TitleWatcher watcher(contents, expected_title);
   watcher.AlsoWaitForTitle(failure_title);
   GURL url = test_server()->GetURL(
       "files/extensions/api_test/webstore_private/noframe2.html");
   ui_test_utils::NavigateToURL(browser(), url);
-  string16 final_title = watcher.WaitAndGetTitle();
+  base::string16 final_title = watcher.WaitAndGetTitle();
   EXPECT_EQ(expected_title, final_title);
 }
 
diff --git a/chrome/browser/extensions/bundle_installer.cc b/chrome/browser/extensions/bundle_installer.cc
index 4f5f7e3..f9a2189 100644
--- a/chrome/browser/extensions/bundle_installer.cc
+++ b/chrome/browser/extensions/bundle_installer.cc
@@ -97,7 +97,7 @@ void BundleInstaller::SetAutoApproveForTesting(bool auto_approve) {
 BundleInstaller::Item::Item() : state(STATE_PENDING) {}
 
 string16 BundleInstaller::Item::GetNameForDisplay() {
-  string16 name = UTF8ToUTF16(localized_name);
+  base::string16 name = UTF8ToUTF16(localized_name);
   base::i18n::AdjustStringForLocaleDirection(&name);
   return l10n_util::GetStringFUTF16(IDS_EXTENSION_PERMISSION_LINE, name);
 }
@@ -182,7 +182,7 @@ string16 BundleInstaller::GetHeadingTextFor(Item::State state) const {
   if (state == Item::STATE_FAILED) {
     if (GetItemsWithState(state).size())
       return l10n_util::GetStringUTF16(IDS_EXTENSION_BUNDLE_ERROR_HEADING);
-    return string16();
+    return base::string16();
   }
 
   size_t total = GetItemsWithState(state).size();
@@ -198,7 +198,7 @@ string16 BundleInstaller::GetHeadingTextFor(Item::State state) const {
 
   int msg_id = kHeadingIds[state][index];
   if (!msg_id)
-    return string16();
+    return base::string16();
 
   return l10n_util::GetStringUTF16(msg_id);
 }
diff --git a/chrome/browser/extensions/bundle_installer.h b/chrome/browser/extensions/bundle_installer.h
index 492490c..2edda54 100644
--- a/chrome/browser/extensions/bundle_installer.h
+++ b/chrome/browser/extensions/bundle_installer.h
@@ -69,7 +69,7 @@ class BundleInstaller : public WebstoreInstallHelper::Delegate,
     Item();
 
     // Gets the localized name, formatted for display in the prompt or bubble.
-    string16 GetNameForDisplay();
+    base::string16 GetNameForDisplay();
 
     std::string id;
     std::string manifest;
@@ -109,7 +109,7 @@ class BundleInstaller : public WebstoreInstallHelper::Delegate,
   //   STATE_PENDING   - install prompt
   //   STATE_INSTALLED - installed bubble successful installs list
   //   STATE_FAILED    - installed bubble failed installs list
-  string16 GetHeadingTextFor(Item::State state) const;
+  base::string16 GetHeadingTextFor(Item::State state) const;
 
  private:
   friend class base::RefCountedThreadSafe<BundleInstaller>;
diff --git a/chrome/browser/extensions/context_menu_matcher.cc b/chrome/browser/extensions/context_menu_matcher.cc
index 80f7bd7..6f03d6a 100644
--- a/chrome/browser/extensions/context_menu_matcher.cc
+++ b/chrome/browser/extensions/context_menu_matcher.cc
@@ -27,10 +27,10 @@ ContextMenuMatcher::ContextMenuMatcher(
       filter_(filter) {
 }
 
-void ContextMenuMatcher::AppendExtensionItems(const std::string& extension_id,
-                                              const string16& selection_text,
-                                              int* index)
-{
+void ContextMenuMatcher::AppendExtensionItems(
+    const std::string& extension_id,
+    const base::string16& selection_text,
+    int* index) {
   DCHECK_GE(*index, 0);
   int max_index =
       IDC_EXTENSIONS_CONTEXT_CUSTOM_LAST - IDC_EXTENSIONS_CONTEXT_CUSTOM_FIRST;
@@ -61,7 +61,7 @@ void ContextMenuMatcher::AppendExtensionItems(const std::string& extension_id,
                                     menu_model_, index);
   } else {
     int menu_id = IDC_EXTENSIONS_CONTEXT_CUSTOM_FIRST + (*index)++;
-    string16 title;
+    base::string16 title;
     MenuItem::List submenu_items;
 
     if (items.size() > 1 || items[0]->type() != MenuItem::NORMAL) {
@@ -97,7 +97,7 @@ void ContextMenuMatcher::Clear() {
 
 base::string16 ContextMenuMatcher::GetTopLevelContextMenuTitle(
     const std::string& extension_id,
-    const string16& selection_text) {
+    const base::string16& selection_text) {
   const Extension* extension = NULL;
   MenuItem::List items;
   bool can_cross_incognito;
@@ -189,7 +189,7 @@ MenuItem::List ContextMenuMatcher::GetRelevantExtensionItems(
 void ContextMenuMatcher::RecursivelyAppendExtensionItems(
     const MenuItem::List& items,
     bool can_cross_incognito,
-    const string16& selection_text,
+    const base::string16& selection_text,
     ui::SimpleMenuModel* menu_model,
     int* index)
 {
@@ -212,7 +212,7 @@ void ContextMenuMatcher::RecursivelyAppendExtensionItems(
     if (menu_id >= IDC_EXTENSIONS_CONTEXT_CUSTOM_LAST)
       return;
     extension_item_map_[menu_id] = item->id();
-    string16 title = item->TitleWithReplacement(selection_text,
+    base::string16 title = item->TitleWithReplacement(selection_text,
                                                 kMaxExtensionItemTitleLength);
     if (item->type() == MenuItem::NORMAL) {
       MenuItem::List children =
diff --git a/chrome/browser/extensions/context_menu_matcher.h b/chrome/browser/extensions/context_menu_matcher.h
index d375163..51707af 100644
--- a/chrome/browser/extensions/context_menu_matcher.h
+++ b/chrome/browser/extensions/context_menu_matcher.h
@@ -35,15 +35,16 @@ class ContextMenuMatcher {
   // The |index| parameter is used for assigning id's, and is incremented for
   // each item actually added.
   void AppendExtensionItems(const std::string& extension_id,
-                            const string16& selection_text,
+                            const base::string16& selection_text,
                             int* index);
 
   void Clear();
 
   // This function returns the top level context menu title of an extension
   // based on a printable selection text.
-  base::string16 GetTopLevelContextMenuTitle(const std::string& extension_id,
-                                             const string16& selection_text);
+  base::string16 GetTopLevelContextMenuTitle(
+      const std::string& extension_id,
+      const base::string16& selection_text);
 
   bool IsCommandIdChecked(int command_id) const;
   bool IsCommandIdEnabled(int command_id) const;
@@ -67,7 +68,7 @@ class ContextMenuMatcher {
   // Used for recursively adding submenus of extension items.
   void RecursivelyAppendExtensionItems(const MenuItem::List& items,
                                        bool can_cross_incognito,
-                                       const string16& selection_text,
+                                       const base::string16& selection_text,
                                        ui::SimpleMenuModel* menu_model,
                                        int* index);
 
diff --git a/chrome/browser/extensions/convert_user_script.cc b/chrome/browser/extensions/convert_user_script.cc
index ef29c3b..9725a64 100644
--- a/chrome/browser/extensions/convert_user_script.cc
+++ b/chrome/browser/extensions/convert_user_script.cc
@@ -32,7 +32,7 @@ namespace values = manifest_values;
 
 scoped_refptr<Extension> ConvertUserScriptToExtension(
     const base::FilePath& user_script_path, const GURL& original_url,
-    const base::FilePath& extensions_dir, string16* error) {
+    const base::FilePath& extensions_dir, base::string16* error) {
   std::string content;
   if (!base::ReadFileToString(user_script_path, &content)) {
     *error = ASCIIToUTF16("Could not read source file.");
@@ -171,7 +171,7 @@ scoped_refptr<Extension> ConvertUserScriptToExtension(
   }
 
   // TODO(rdevlin.cronin): Continue removing std::string errors and replacing
-  // with string16
+  // with base::string16
   std::string utf8_error;
   scoped_refptr<Extension> extension = Extension::Create(
       temp_dir.path(),
diff --git a/chrome/browser/extensions/convert_user_script.h b/chrome/browser/extensions/convert_user_script.h
index 1ce8936..1a910a0 100644
--- a/chrome/browser/extensions/convert_user_script.h
+++ b/chrome/browser/extensions/convert_user_script.h
@@ -28,7 +28,7 @@ class Extension;
 // returned object.
 scoped_refptr<extensions::Extension> ConvertUserScriptToExtension(
     const base::FilePath& user_script, const GURL& original_url,
-    const base::FilePath& extensions_dir, string16* error);
+    const base::FilePath& extensions_dir, base::string16* error);
 
 }  // namespace extensions
 
diff --git a/chrome/browser/extensions/convert_user_script_unittest.cc b/chrome/browser/extensions/convert_user_script_unittest.cc
index d0e5e95..e0e8ac7 100644
--- a/chrome/browser/extensions/convert_user_script_unittest.cc
+++ b/chrome/browser/extensions/convert_user_script_unittest.cc
@@ -41,7 +41,7 @@ TEST_F(ExtensionFromUserScript, Basic) {
   test_file = test_file.AppendASCII("extensions")
                        .AppendASCII("user_script_basic.user.js");
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo"),
       extensions_dir.path(), &error));
@@ -94,7 +94,7 @@ TEST_F(ExtensionFromUserScript, NoMetadata) {
   test_file = test_file.AppendASCII("extensions")
                        .AppendASCII("user_script_no_metadata.user.js");
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo/bar.user.js?monkey"),
       extensions_dir.path(), &error));
@@ -143,7 +143,7 @@ TEST_F(ExtensionFromUserScript, NotUTF8) {
   test_file = test_file.AppendASCII("extensions")
                        .AppendASCII("user_script_not_utf8.user.js");
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo/bar.user.js?monkey"),
       extensions_dir.path(), &error));
@@ -161,7 +161,7 @@ TEST_F(ExtensionFromUserScript, RunAtDocumentStart) {
   test_file = test_file.AppendASCII("extensions")
                        .AppendASCII("user_script_run_at_start.user.js");
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo"),
       extensions_dir.path(), &error));
@@ -196,7 +196,7 @@ TEST_F(ExtensionFromUserScript, RunAtDocumentEnd) {
   test_file = test_file.AppendASCII("extensions")
                        .AppendASCII("user_script_run_at_end.user.js");
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo"),
       extensions_dir.path(), &error));
@@ -232,7 +232,7 @@ TEST_F(ExtensionFromUserScript, RunAtDocumentIdle) {
                        .AppendASCII("user_script_run_at_idle.user.js");
   ASSERT_TRUE(base::PathExists(test_file)) << test_file.value();
 
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(ConvertUserScriptToExtension(
       test_file, GURL("http://www.google.com/foo"),
       extensions_dir.path(), &error));
diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index 85109f56..cdc45e5 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -206,7 +206,7 @@ void CrxInstaller::InstallUserScript(const base::FilePath& source_file,
 }
 
 void CrxInstaller::ConvertUserScriptOnFileThread() {
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension = ConvertUserScriptToExtension(
       source_file_, download_url_, install_directory_, &error);
   if (!extension.get()) {
@@ -231,7 +231,7 @@ void CrxInstaller::InstallWebApp(const WebApplicationInfo& web_app) {
 void CrxInstaller::ConvertWebAppOnFileThread(
     const WebApplicationInfo& web_app,
     const base::FilePath& install_directory) {
-  string16 error;
+  base::string16 error;
   scoped_refptr<Extension> extension(
       ConvertWebAppToExtension(web_app, base::Time::Now(), install_directory));
   if (!extension.get()) {
@@ -416,7 +416,7 @@ CrxInstallerError CrxInstaller::AllowInstall(const Extension* extension) {
   return CrxInstallerError();
 }
 
-void CrxInstaller::OnUnpackFailure(const string16& error_message) {
+void CrxInstaller::OnUnpackFailure(const base::string16& error_message) {
   DCHECK(installer_task_runner_->RunsTasksOnCurrentThread());
 
   UMA_HISTOGRAM_ENUMERATION("Extensions.UnpackFailureInstallSource",
@@ -564,7 +564,7 @@ void CrxInstaller::ConfirmInstall() {
     }
   }
 
-  string16 error = installer_.CheckManagementPolicy();
+  base::string16 error = installer_.CheckManagementPolicy();
   if (!error.empty()) {
     // We don't want to show the error infobar for installs from the WebStore,
     // because the WebStore already shows an error dialog itself.
@@ -695,7 +695,7 @@ void CrxInstaller::CompleteInstall() {
   // TODO(aa): All paths to resources inside extensions should be created
   // lazily and based on the Extension's root path at that moment.
   // TODO(rdevlin.cronin): Continue removing std::string errors and replacing
-  // with string16
+  // with base::string16
   std::string extension_id = extension()->id();
   std::string error;
   installer_.set_extension(extension_file_util::LoadExtension(
@@ -729,7 +729,7 @@ void CrxInstaller::ReportFailureFromUIThread(const CrxInstallerError& error) {
       content::NotificationService::current();
   service->Notify(chrome::NOTIFICATION_EXTENSION_INSTALL_ERROR,
                   content::Source<CrxInstaller>(this),
-                  content::Details<const string16>(&error.message()));
+                  content::Details<const base::string16>(&error.message()));
 
   // This isn't really necessary, it is only used because unit tests expect to
   // see errors get reported via this interface.
diff --git a/chrome/browser/extensions/crx_installer.h b/chrome/browser/extensions/crx_installer.h
index b213a3f..ce6d2df 100644
--- a/chrome/browser/extensions/crx_installer.h
+++ b/chrome/browser/extensions/crx_installer.h
@@ -219,7 +219,7 @@ class CrxInstaller
   CrxInstallerError AllowInstall(const Extension* extension);
 
   // SandboxedUnpackerClient
-  virtual void OnUnpackFailure(const string16& error_message) OVERRIDE;
+  virtual void OnUnpackFailure(const base::string16& error_message) OVERRIDE;
   virtual void OnUnpackSuccess(const base::FilePath& temp_dir,
                                const base::FilePath& extension_dir,
                                const base::DictionaryValue* original_manifest,
diff --git a/chrome/browser/extensions/crx_installer_browsertest.cc b/chrome/browser/extensions/crx_installer_browsertest.cc
index 3e5bd6f..5ef3f3e 100644
--- a/chrome/browser/extensions/crx_installer_browsertest.cc
+++ b/chrome/browser/extensions/crx_installer_browsertest.cc
@@ -52,7 +52,7 @@ class MockPromptProxy :
   bool did_succeed() const { return !extension_id_.empty(); }
   const std::string& extension_id() { return extension_id_; }
   bool confirmation_requested() const { return confirmation_requested_; }
-  const string16& error() const { return error_; }
+  const base::string16& error() const { return error_; }
 
   // To have any effect, this should be called before CreatePrompt.
   void set_record_oauth2_grant(bool record_oauth2_grant) {
@@ -61,7 +61,7 @@ class MockPromptProxy :
 
   void set_extension_id(const std::string& id) { extension_id_ = id; }
   void set_confirmation_requested() { confirmation_requested_ = true; }
-  void set_error(const string16& error) { error_ = error; }
+  void set_error(const base::string16& error) { error_ = error; }
 
   scoped_ptr<ExtensionInstallPrompt> CreatePrompt();
 
@@ -76,7 +76,7 @@ class MockPromptProxy :
   // Data reported back to us by the prompt we created.
   bool confirmation_requested_;
   std::string extension_id_;
-  string16 error_;
+  base::string16 error_;
 };
 
 class MockInstallPrompt : public ExtensionInstallPrompt {
diff --git a/chrome/browser/extensions/crx_installer_error.h b/chrome/browser/extensions/crx_installer_error.h
index 41990af..730a9e3 100644
--- a/chrome/browser/extensions/crx_installer_error.h
+++ b/chrome/browser/extensions/crx_installer_error.h
@@ -22,21 +22,21 @@ class CrxInstallerError {
   CrxInstallerError() : type_(ERROR_NONE) {
   }
 
-  explicit CrxInstallerError(const string16& message)
+  explicit CrxInstallerError(const base::string16& message)
       : type_(message.empty() ? ERROR_NONE : ERROR_OTHER),
         message_(message) {
   }
 
-  CrxInstallerError(Type type, const string16& message)
+  CrxInstallerError(Type type, const base::string16& message)
       : type_(type), message_(message) {
   }
 
   Type type() const { return type_; }
-  const string16& message() const { return message_; }
+  const base::string16& message() const { return message_; }
 
  private:
   Type type_;
-  string16 message_;
+  base::string16 message_;
 };
 
 }  // namespace extensions
diff --git a/chrome/browser/extensions/error_console/error_console_unittest.cc b/chrome/browser/extensions/error_console/error_console_unittest.cc
index 501e7aa..c0a386c 100644
--- a/chrome/browser/extensions/error_console/error_console_unittest.cc
+++ b/chrome/browser/extensions/error_console/error_console_unittest.cc
@@ -49,7 +49,7 @@ string16 GetSourceForExtensionId(const std::string& extension_id) {
 scoped_ptr<ExtensionError> CreateNewRuntimeError(
     bool from_incognito,
     const std::string& extension_id,
-    const string16& message) {
+    const base::string16& message) {
   return scoped_ptr<ExtensionError>(new RuntimeError(
       extension_id,
       from_incognito,
@@ -117,7 +117,7 @@ TEST_F(ErrorConsoleUnitTest, AddAndRemoveErrors) {
   // Add another error for a different extension id.
   const std::string kSecondId = id_util::GenerateId("id2");
   error_console_->ReportError(
-      CreateNewRuntimeError(false, kSecondId, string16()));
+      CreateNewRuntimeError(false, kSecondId, base::string16()));
 
   // There should be two entries now, one for each id, and there should be one
   // error for the second extension.
diff --git a/chrome/browser/extensions/extension_context_menu_browsertest.cc b/chrome/browser/extensions/extension_context_menu_browsertest.cc
index c52506b..616465a 100644
--- a/chrome/browser/extensions/extension_context_menu_browsertest.cc
+++ b/chrome/browser/extensions/extension_context_menu_browsertest.cc
@@ -205,12 +205,12 @@ class ExtensionContextMenuBrowserTest : public ExtensionBrowserTest {
 
  bool MenuHasExtensionItemWithLabel(TestRenderViewContextMenu* menu,
                                      const std::string& label) {
-    string16 label16 = UTF8ToUTF16(label);
+    base::string16 label16 = UTF8ToUTF16(label);
     std::map<int, MenuItem::Id>::iterator i;
     for (i = menu->extension_items().extension_item_map_.begin();
          i != menu->extension_items().extension_item_map_.end(); ++i) {
       const MenuItem::Id& id = i->second;
-      string16 tmp_label;
+      base::string16 tmp_label;
       EXPECT_TRUE(GetItemLabel(menu, id, &tmp_label));
       if (tmp_label == label16)
         return true;
@@ -223,7 +223,7 @@ class ExtensionContextMenuBrowserTest : public ExtensionBrowserTest {
   // false.
   bool GetItemLabel(TestRenderViewContextMenu* menu,
                     const MenuItem::Id& id,
-                    string16* result) {
+                    base::string16* result) {
     int command_id = 0;
     if (!FindCommandId(menu, id, &command_id))
       return false;
@@ -333,7 +333,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionContextMenuBrowserTest, LongTitle) {
   scoped_ptr<TestRenderViewContextMenu> menu(
       CreateMenu(browser(), url, GURL(), GURL()));
 
-  string16 label;
+  base::string16 label;
   ASSERT_TRUE(GetItemLabel(menu.get(), item->id(), &label));
   ASSERT_TRUE(label.size() <= limit);
 }
@@ -472,7 +472,7 @@ IN_PROC_BROWSER_TEST_F(ExtensionContextMenuBrowserTest, Separators) {
   // name.
   MenuModel* model = NULL;
   int index = 0;
-  string16 label;
+  base::string16 label;
   ASSERT_TRUE(menu->GetMenuModelAndItemIndex(
       IDC_EXTENSIONS_CONTEXT_CUSTOM_FIRST, &model, &index));
   EXPECT_EQ(UTF8ToUTF16(extension->name()), model->GetLabelAt(index));
diff --git a/chrome/browser/extensions/extension_disabled_ui.cc b/chrome/browser/extensions/extension_disabled_ui.cc
index 4a5c3d9..a5560ab 100644
--- a/chrome/browser/extensions/extension_disabled_ui.cc
+++ b/chrome/browser/extensions/extension_disabled_ui.cc
@@ -148,13 +148,13 @@ class ExtensionDisabledGlobalError : public GlobalErrorWithStandardBubble,
   virtual Severity GetSeverity() OVERRIDE;
   virtual bool HasMenuItem() OVERRIDE;
   virtual int MenuItemCommandID() OVERRIDE;
-  virtual string16 MenuItemLabel() OVERRIDE;
+  virtual base::string16 MenuItemLabel() OVERRIDE;
   virtual void ExecuteMenuItem(Browser* browser) OVERRIDE;
   virtual gfx::Image GetBubbleViewIcon() OVERRIDE;
-  virtual string16 GetBubbleViewTitle() OVERRIDE;
+  virtual base::string16 GetBubbleViewTitle() OVERRIDE;
   virtual std::vector<string16> GetBubbleViewMessages() OVERRIDE;
-  virtual string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
-  virtual string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
   virtual void OnBubbleViewDidClose(Browser* browser) OVERRIDE;
   virtual void BubbleViewAcceptButtonPressed(Browser* browser) OVERRIDE;
   virtual void BubbleViewCancelButtonPressed(Browser* browser) OVERRIDE;
diff --git a/chrome/browser/extensions/extension_error_reporter.cc b/chrome/browser/extensions/extension_error_reporter.cc
index 669abb1..618a8c8 100644
--- a/chrome/browser/extensions/extension_error_reporter.cc
+++ b/chrome/browser/extensions/extension_error_reporter.cc
@@ -35,7 +35,7 @@ ExtensionErrorReporter::ExtensionErrorReporter(bool enable_noisy_errors)
 
 ExtensionErrorReporter::~ExtensionErrorReporter() {}
 
-void ExtensionErrorReporter::ReportError(const string16& message,
+void ExtensionErrorReporter::ReportError(const base::string16& message,
                                          bool be_noisy) {
   // NOTE: There won't be a ui_loop_ in the unit test environment.
   if (ui_loop_ && base::MessageLoop::current() != ui_loop_) {
diff --git a/chrome/browser/extensions/extension_error_reporter.h b/chrome/browser/extensions/extension_error_reporter.h
index 058b027..f2ee723 100644
--- a/chrome/browser/extensions/extension_error_reporter.h
+++ b/chrome/browser/extensions/extension_error_reporter.h
@@ -33,7 +33,7 @@ class ExtensionErrorReporter {
 
   // Report an error. Errors always go to VLOG(1). Optionally, they can also
   // cause a noisy alert box. This method can be called from any thread.
-  void ReportError(const string16& message, bool be_noisy);
+  void ReportError(const base::string16& message, bool be_noisy);
 
   // Get the errors that have been reported so far.
   const std::vector<string16>* GetErrors();
diff --git a/chrome/browser/extensions/extension_error_ui.cc b/chrome/browser/extensions/extension_error_ui.cc
index 5412b90..96603e6 100644
--- a/chrome/browser/extensions/extension_error_ui.cc
+++ b/chrome/browser/extensions/extension_error_ui.cc
@@ -40,7 +40,7 @@ string16 ExtensionErrorUI::GenerateMessageSection(
   CHECK(extensions);
   CHECK(extension_template_message_id);
   CHECK(app_template_message_id);
-  string16 message;
+  base::string16 message;
 
   for (ExtensionIdSet::const_iterator iter = extensions->begin();
        iter != extensions->end(); ++iter) {
diff --git a/chrome/browser/extensions/extension_error_ui.h b/chrome/browser/extensions/extension_error_ui.h
index d70fa1a..362c2df 100644
--- a/chrome/browser/extensions/extension_error_ui.h
+++ b/chrome/browser/extensions/extension_error_ui.h
@@ -56,10 +56,10 @@ class ExtensionErrorUI {
   ExtensionService* extension_service() const { return extension_service_; }
 
   // Model methods for the bubble view.
-  string16 GetBubbleViewTitle();
+  base::string16 GetBubbleViewTitle();
   std::vector<string16> GetBubbleViewMessages();
-  string16 GetBubbleViewAcceptButtonLabel();
-  string16 GetBubbleViewCancelButtonLabel();
+  base::string16 GetBubbleViewAcceptButtonLabel();
+  base::string16 GetBubbleViewCancelButtonLabel();
 
   // Sub-classes should call this methods based on the actions taken by the user
   // in the error bubble.
@@ -72,16 +72,17 @@ class ExtensionErrorUI {
   ExtensionService* extension_service_;
   scoped_ptr<extensions::ExtensionIdSet> external_extension_ids_;
   scoped_ptr<extensions::ExtensionIdSet> blacklisted_extension_ids_;
-  string16 message_;  // Displayed in the body of the alert.
+  base::string16 message_;  // Displayed in the body of the alert.
 
   // For a given set of extension IDs, generates appropriate text
   // describing what the user needs to know about them.
-  string16 GenerateMessageSection(const extensions::ExtensionIdSet* extensions,
-                                  int extension_template_message_id,
-                                  int app_template_message_id);
+  base::string16 GenerateMessageSection(
+      const extensions::ExtensionIdSet* extensions,
+      int extension_template_message_id,
+      int app_template_message_id);
 
   // Generates the message displayed in the body of the alert.
-  string16 GenerateMessage();
+  base::string16 GenerateMessage();
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionErrorUI);
 };
diff --git a/chrome/browser/extensions/extension_error_ui_default.h b/chrome/browser/extensions/extension_error_ui_default.h
index dab1444..8475cb6 100644
--- a/chrome/browser/extensions/extension_error_ui_default.h
+++ b/chrome/browser/extensions/extension_error_ui_default.h
@@ -33,12 +33,12 @@ class ExtensionErrorUIDefault : public ExtensionErrorUI {
     // GlobalError methods.
     virtual bool HasMenuItem() OVERRIDE;
     virtual int MenuItemCommandID() OVERRIDE;
-    virtual string16 MenuItemLabel() OVERRIDE;
+    virtual base::string16 MenuItemLabel() OVERRIDE;
     virtual void ExecuteMenuItem(Browser* browser) OVERRIDE;
-    virtual string16 GetBubbleViewTitle() OVERRIDE;
+    virtual base::string16 GetBubbleViewTitle() OVERRIDE;
     virtual std::vector<string16> GetBubbleViewMessages() OVERRIDE;
-    virtual string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
-    virtual string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
+    virtual base::string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
+    virtual base::string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
     virtual void OnBubbleViewDidClose(Browser* browser) OVERRIDE;
     virtual void BubbleViewAcceptButtonPressed(Browser* browser) OVERRIDE;
     virtual void BubbleViewCancelButtonPressed(Browser* browser) OVERRIDE;
diff --git a/chrome/browser/extensions/extension_install_prompt.h b/chrome/browser/extensions/extension_install_prompt.h
index 35ecc2a5..772b66c 100644
--- a/chrome/browser/extensions/extension_install_prompt.h
+++ b/chrome/browser/extensions/extension_install_prompt.h
@@ -97,16 +97,16 @@ class ExtensionInstallPrompt
     void set_type(PromptType type) { type_ = type; }
 
     // Getters for UI element labels.
-    string16 GetDialogTitle() const;
-    string16 GetHeading() const;
+    base::string16 GetDialogTitle() const;
+    base::string16 GetHeading() const;
     int GetDialogButtons() const;
     bool HasAcceptButtonLabel() const;
-    string16 GetAcceptButtonLabel() const;
+    base::string16 GetAcceptButtonLabel() const;
     bool HasAbortButtonLabel() const;
-    string16 GetAbortButtonLabel() const;
-    string16 GetPermissionsHeading() const;
-    string16 GetOAuthHeading() const;
-    string16 GetRetainedFilesHeading() const;
+    base::string16 GetAbortButtonLabel() const;
+    base::string16 GetPermissionsHeading() const;
+    base::string16 GetOAuthHeading() const;
+    base::string16 GetRetainedFilesHeading() const;
 
     bool ShouldShowPermissions() const;
 
@@ -119,17 +119,17 @@ class ExtensionInstallPrompt
     // that they append to the star display area.
     typedef void(*StarAppender)(const gfx::ImageSkia*, void*);
     void AppendRatingStars(StarAppender appender, void* data) const;
-    string16 GetRatingCount() const;
-    string16 GetUserCount() const;
+    base::string16 GetRatingCount() const;
+    base::string16 GetUserCount() const;
     size_t GetPermissionCount() const;
     size_t GetPermissionsDetailsCount() const;
-    string16 GetPermission(size_t index) const;
-    string16 GetPermissionsDetails(size_t index) const;
+    base::string16 GetPermission(size_t index) const;
+    base::string16 GetPermissionsDetails(size_t index) const;
     bool GetIsShowingDetails(DetailsType type, size_t index) const;
     size_t GetOAuthIssueCount() const;
     const IssueAdviceInfoEntry& GetOAuthIssue(size_t index) const;
     size_t GetRetainedFileCount() const;
-    string16 GetRetainedFile(size_t index) const;
+    base::string16 GetRetainedFile(size_t index) const;
 
     // Populated for BUNDLE_INSTALL_PROMPT.
     const extensions::BundleInstaller* bundle() const { return bundle_; }
@@ -169,7 +169,7 @@ class ExtensionInstallPrompt
     IssueAdviceInfo oauth_issue_advice_;
 
     // User name to be used in Oauth heading label.
-    string16 oauth_user_name_;
+    base::string16 oauth_user_name_;
 
     // The extension or bundle being installed.
     const extensions::Extension* extension_;
diff --git a/chrome/browser/extensions/extension_installer.cc b/chrome/browser/extensions/extension_installer.cc
index 7d47df1..b6dae68 100644
--- a/chrome/browser/extensions/extension_installer.cc
+++ b/chrome/browser/extensions/extension_installer.cc
@@ -28,7 +28,7 @@ void ExtensionInstaller::CheckRequirements(
 }
 
 string16 ExtensionInstaller::CheckManagementPolicy() {
-  string16 error;
+  base::string16 error;
   bool allowed = ExtensionSystem::Get(profile_)->management_policy()
       ->UserMayLoad(extension_.get(), &error);
   DCHECK(allowed || !error.empty());
diff --git a/chrome/browser/extensions/extension_installer.h b/chrome/browser/extensions/extension_installer.h
index 13170cb..e72e01b 100644
--- a/chrome/browser/extensions/extension_installer.h
+++ b/chrome/browser/extensions/extension_installer.h
@@ -35,7 +35,7 @@ class ExtensionInstaller {
   void CheckRequirements(const RequirementsCallback& callback);
 
   // Checks the management policy if the extension can be installed.
-  string16 CheckManagementPolicy();
+  base::string16 CheckManagementPolicy();
 
   Profile* profile() const {
     return profile_;
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index f8245a5..e010bbb 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -168,12 +168,12 @@ class SharedModuleProvider : public extensions::ManagementPolicy::Provider {
   }
 
   virtual bool UserMayModifySettings(const Extension* extension,
-                                     string16* error) const OVERRIDE {
+                                     base::string16* error) const OVERRIDE {
     return !IsCWSSharedModule(extension);
   }
 
   virtual bool MustRemainEnabled(const Extension* extension,
-                                 string16* error) const OVERRIDE {
+                                 base::string16* error) const OVERRIDE {
     return IsCWSSharedModule(extension);
   }
 
@@ -296,7 +296,7 @@ bool ExtensionService::UninstallExtensionHelper(
 
   // The following call to UninstallExtension will not allow an uninstall of a
   // policy-controlled extension.
-  string16 error;
+  base::string16 error;
   if (!extensions_service->UninstallExtension(extension_id, false, &error)) {
     LOG(WARNING) << "Cannot uninstall extension with id " << extension_id
                  << ": " << error;
@@ -745,7 +745,7 @@ void ExtensionService::ReloadExtension(const std::string extension_id) {
 bool ExtensionService::UninstallExtension(
     std::string extension_id,
     bool external_uninstall,
-    string16* error) {
+    base::string16* error) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   scoped_refptr<const Extension> extension(GetInstalledExtension(extension_id));
@@ -2418,7 +2418,7 @@ void ExtensionService::ReportExtensionLoadError(
       content::Details<const std::string>(&error));
 
   std::string path_str = UTF16ToUTF8(extension_path.LossyDisplayName());
-  string16 message = UTF8ToUTF16(base::StringPrintf(
+  base::string16 message = UTF8ToUTF16(base::StringPrintf(
       "Could not load extension from '%s'. %s",
       path_str.c_str(), error.c_str()));
   ExtensionErrorReporter::GetInstance()->ReportError(message, be_noisy);
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 2d2adb9..e9e38b6 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -268,7 +268,7 @@ class ExtensionService
   // to ExtensionPrefs some other way.
   virtual bool UninstallExtension(std::string extension_id,
                                   bool external_uninstall,
-                                  string16* error);
+                                  base::string16* error);
 
   virtual bool IsExtensionEnabled(
       const std::string& extension_id) const OVERRIDE;
diff --git a/chrome/browser/extensions/extension_service_unittest.cc b/chrome/browser/extensions/extension_service_unittest.cc
index 70d2121..7d23c2f 100644
--- a/chrome/browser/extensions/extension_service_unittest.cc
+++ b/chrome/browser/extensions/extension_service_unittest.cc
@@ -4265,8 +4265,8 @@ TEST_F(ExtensionServiceTest, ClearExtensionData) {
   webkit_database::DatabaseTracker* db_tracker =
       BrowserContext::GetDefaultStoragePartition(profile_.get())->
           GetDatabaseTracker();
-  string16 db_name = UTF8ToUTF16("db");
-  string16 description = UTF8ToUTF16("db_description");
+  base::string16 db_name = UTF8ToUTF16("db");
+  base::string16 description = UTF8ToUTF16("db_description");
   int64 size;
   db_tracker->DatabaseOpened(origin_id, db_name, description, 1, &size);
   db_tracker->DatabaseClosed(origin_id, db_name);
@@ -4381,8 +4381,8 @@ TEST_F(ExtensionServiceTest, ClearAppData) {
   webkit_database::DatabaseTracker* db_tracker =
       BrowserContext::GetDefaultStoragePartition(profile_.get())->
           GetDatabaseTracker();
-  string16 db_name = UTF8ToUTF16("db");
-  string16 description = UTF8ToUTF16("db_description");
+  base::string16 db_name = UTF8ToUTF16("db");
+  base::string16 description = UTF8ToUTF16("db_description");
   int64 size;
   db_tracker->DatabaseOpened(origin_id, db_name, description, 1, &size);
   db_tracker->DatabaseClosed(origin_id, db_name);
diff --git a/chrome/browser/extensions/extension_warning_badge_service.cc b/chrome/browser/extensions/extension_warning_badge_service.cc
index 3ef80c4..c465d04 100644
--- a/chrome/browser/extensions/extension_warning_badge_service.cc
+++ b/chrome/browser/extensions/extension_warning_badge_service.cc
@@ -28,7 +28,7 @@ class ErrorBadge : public GlobalError {
   // Implementation for GlobalError:
   virtual bool HasMenuItem() OVERRIDE;
   virtual int MenuItemCommandID() OVERRIDE;
-  virtual string16 MenuItemLabel() OVERRIDE;
+  virtual base::string16 MenuItemLabel() OVERRIDE;
   virtual void ExecuteMenuItem(Browser* browser) OVERRIDE;
 
   virtual bool HasBubbleView() OVERRIDE;
diff --git a/chrome/browser/extensions/external_install_ui.cc b/chrome/browser/extensions/external_install_ui.cc
index b5ac233..0e50729 100644
--- a/chrome/browser/extensions/external_install_ui.cc
+++ b/chrome/browser/extensions/external_install_ui.cc
@@ -103,13 +103,13 @@ class ExternalInstallMenuAlert : public GlobalErrorWithStandardBubble,
   virtual Severity GetSeverity() OVERRIDE;
   virtual bool HasMenuItem() OVERRIDE;
   virtual int MenuItemCommandID() OVERRIDE;
-  virtual string16 MenuItemLabel() OVERRIDE;
+  virtual base::string16 MenuItemLabel() OVERRIDE;
   virtual void ExecuteMenuItem(Browser* browser) OVERRIDE;
   virtual bool HasBubbleView() OVERRIDE;
-  virtual string16 GetBubbleViewTitle() OVERRIDE;
+  virtual base::string16 GetBubbleViewTitle() OVERRIDE;
   virtual std::vector<string16> GetBubbleViewMessages() OVERRIDE;
-  virtual string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
-  virtual string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
   virtual void OnBubbleViewDidClose(Browser* browser) OVERRIDE;
   virtual void BubbleViewAcceptButtonPressed(Browser* browser) OVERRIDE;
   virtual void BubbleViewCancelButtonPressed(Browser* browser) OVERRIDE;
@@ -137,10 +137,10 @@ class ExternalInstallGlobalError : public ExternalInstallMenuAlert {
   virtual void ExecuteMenuItem(Browser* browser) OVERRIDE;
   virtual bool HasBubbleView() OVERRIDE;
   virtual gfx::Image GetBubbleViewIcon() OVERRIDE;
-  virtual string16 GetBubbleViewTitle() OVERRIDE;
+  virtual base::string16 GetBubbleViewTitle() OVERRIDE;
   virtual std::vector<string16> GetBubbleViewMessages() OVERRIDE;
-  virtual string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
-  virtual string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewAcceptButtonLabel() OVERRIDE;
+  virtual base::string16 GetBubbleViewCancelButtonLabel() OVERRIDE;
   virtual void OnBubbleViewDidClose(Browser* browser) OVERRIDE;
   virtual void BubbleViewAcceptButtonPressed(Browser* browser) OVERRIDE;
   virtual void BubbleViewCancelButtonPressed(Browser* browser) OVERRIDE;
@@ -282,7 +282,7 @@ bool ExternalInstallMenuAlert::HasBubbleView() {
   return false;
 }
 string16 ExternalInstallMenuAlert::GetBubbleViewTitle() {
-  return string16();
+  return base::string16();
 }
 
 std::vector<string16> ExternalInstallMenuAlert::GetBubbleViewMessages() {
@@ -290,11 +290,11 @@ std::vector<string16> ExternalInstallMenuAlert::GetBubbleViewMessages() {
 }
 
 string16 ExternalInstallMenuAlert::GetBubbleViewAcceptButtonLabel() {
-  return string16();
+  return base::string16();
 }
 
 string16 ExternalInstallMenuAlert::GetBubbleViewCancelButtonLabel() {
-  return string16();
+  return base::string16();
 }
 
 void ExternalInstallMenuAlert::OnBubbleViewDidClose(Browser* browser) {
diff --git a/chrome/browser/extensions/external_registry_loader_win.cc b/chrome/browser/extensions/external_registry_loader_win.cc
index 2edf5fa..00366b9 100644
--- a/chrome/browser/extensions/external_registry_loader_win.cc
+++ b/chrome/browser/extensions/external_registry_loader_win.cc
@@ -70,7 +70,7 @@ void ExternalRegistryLoader::LoadOnFileThread() {
   for (std::set<string16>::const_iterator it = keys.begin();
        it != keys.end(); ++it) {
     base::win::RegKey key;
-    string16 key_path = ASCIIToWide(kRegistryExtensions);
+    base::string16 key_path = ASCIIToWide(kRegistryExtensions);
     key_path.append(L"\\");
     key_path.append(*it);
     if (key.Open(HKEY_LOCAL_MACHINE,
@@ -83,7 +83,7 @@ void ExternalRegistryLoader::LoadOnFileThread() {
       }
     }
 
-    string16 extension_path_str;
+    base::string16 extension_path_str;
     if (key.ReadValue(kRegistryExtensionPath, &extension_path_str)
         != ERROR_SUCCESS) {
       // TODO(erikkay): find a way to get this into about:extensions
@@ -115,7 +115,7 @@ void ExternalRegistryLoader::LoadOnFileThread() {
       continue;
     }
 
-    string16 extension_version;
+    base::string16 extension_version;
     if (key.ReadValue(kRegistryExtensionVersion, &extension_version)
         != ERROR_SUCCESS) {
       // TODO(erikkay): find a way to get this into about:extensions
diff --git a/chrome/browser/extensions/install_verifier.cc b/chrome/browser/extensions/install_verifier.cc
index 4b7f347..d235757 100644
--- a/chrome/browser/extensions/install_verifier.cc
+++ b/chrome/browser/extensions/install_verifier.cc
@@ -180,7 +180,7 @@ static bool FromStore(const Extension* extension) {
 
 bool InstallVerifier::MustRemainDisabled(const Extension* extension,
                                          Extension::DisableReason* reason,
-                                         string16* error) const {
+                                         base::string16* error) const {
   if (!ShouldEnforce() || !extension->is_extension() ||
       Manifest::IsUnpackedLocation(extension->location()) ||
       AllowedByEnterprisePolicy(extension->id()))
diff --git a/chrome/browser/extensions/install_verifier.h b/chrome/browser/extensions/install_verifier.h
index 1f209ac..1131e38 100644
--- a/chrome/browser/extensions/install_verifier.h
+++ b/chrome/browser/extensions/install_verifier.h
@@ -68,7 +68,7 @@ class InstallVerifier : public ManagementPolicy::Provider {
   virtual std::string GetDebugPolicyProviderName() const OVERRIDE;
   virtual bool MustRemainDisabled(const Extension* extension,
                                   Extension::DisableReason* reason,
-                                  string16* error) const OVERRIDE;
+                                  base::string16* error) const OVERRIDE;
 
  private:
   // We keep a list of operations to the current set of extensions - either
diff --git a/chrome/browser/extensions/menu_manager.cc b/chrome/browser/extensions/menu_manager.cc
index 909bff0e..298ea34 100644
--- a/chrome/browser/extensions/menu_manager.cc
+++ b/chrome/browser/extensions/menu_manager.cc
@@ -168,8 +168,8 @@ std::set<MenuItem::Id> MenuItem::RemoveAllDescendants() {
 }
 
 string16 MenuItem::TitleWithReplacement(
-    const string16& selection, size_t max_length) const {
-  string16 result = UTF8ToUTF16(title_);
+    const base::string16& selection, size_t max_length) const {
+  base::string16 result = UTF8ToUTF16(title_);
   // TODO(asargent) - Change this to properly handle %% escaping so you can
   // put "%s" in titles that won't get substituted.
   ReplaceSubstringsAfterOffset(&result, 0, ASCIIToUTF16("%s"), selection);
diff --git a/chrome/browser/extensions/menu_manager.h b/chrome/browser/extensions/menu_manager.h
index ac0d7a3..ea6cecf 100644
--- a/chrome/browser/extensions/menu_manager.h
+++ b/chrome/browser/extensions/menu_manager.h
@@ -169,7 +169,7 @@ class MenuItem {
 
   // Returns the title with any instances of %s replaced by |selection|. The
   // result will be no longer than |max_length|.
-  string16 TitleWithReplacement(const string16& selection,
+  base::string16 TitleWithReplacement(const base::string16& selection,
                                 size_t max_length) const;
 
   // Sets the checked state to |checked|. Returns true if successful.
diff --git a/chrome/browser/extensions/menu_manager_unittest.cc b/chrome/browser/extensions/menu_manager_unittest.cc
index e6e8b6c..ea2056e 100644
--- a/chrome/browser/extensions/menu_manager_unittest.cc
+++ b/chrome/browser/extensions/menu_manager_unittest.cc
@@ -620,7 +620,7 @@ TEST_F(MenuManagerTest, ExecuteCommand) {
   ASSERT_TRUE(info->GetString("pageUrl", &tmp));
   ASSERT_EQ(params.page_url.spec(), tmp);
 
-  string16 tmp16;
+  base::string16 tmp16;
   ASSERT_TRUE(info->GetString("selectionText", &tmp16));
   ASSERT_EQ(params.selection_text, tmp16);
 
diff --git a/chrome/browser/extensions/pack_extension_job.cc b/chrome/browser/extensions/pack_extension_job.cc
index da182b1..a1e752f 100644
--- a/chrome/browser/extensions/pack_extension_job.cc
+++ b/chrome/browser/extensions/pack_extension_job.cc
@@ -93,8 +93,8 @@ void PackExtensionJob::ReportFailureOnClientThread(
 string16 PackExtensionJob::StandardSuccessMessage(
     const base::FilePath& crx_file,
     const base::FilePath& key_file) {
-  string16 crx_file_string = crx_file.LossyDisplayName();
-  string16 key_file_string = key_file.LossyDisplayName();
+  base::string16 crx_file_string = crx_file.LossyDisplayName();
+  base::string16 key_file_string = key_file.LossyDisplayName();
   if (key_file_string.empty()) {
     return l10n_util::GetStringFUTF16(
         IDS_EXTENSION_PACK_DIALOG_SUCCESS_BODY_UPDATE,
diff --git a/chrome/browser/extensions/pack_extension_job.h b/chrome/browser/extensions/pack_extension_job.h
index adf21ab..61a48cb 100644
--- a/chrome/browser/extensions/pack_extension_job.h
+++ b/chrome/browser/extensions/pack_extension_job.h
@@ -44,7 +44,7 @@ class PackExtensionJob : public base::RefCountedThreadSafe<PackExtensionJob> {
   void ClearClient();
 
   // The standard packing success message.
-  static string16 StandardSuccessMessage(const base::FilePath& crx_file,
+  static base::string16 StandardSuccessMessage(const base::FilePath& crx_file,
                                          const base::FilePath& key_file);
 
   void set_asynchronous(bool async) { asynchronous_ = async; }
diff --git a/chrome/browser/extensions/sandboxed_unpacker.cc b/chrome/browser/extensions/sandboxed_unpacker.cc
index 34716af..33478d2 100644
--- a/chrome/browser/extensions/sandboxed_unpacker.cc
+++ b/chrome/browser/extensions/sandboxed_unpacker.cc
@@ -368,7 +368,7 @@ void SandboxedUnpacker::OnUnpackExtensionSucceeded(
   // Localize manifest now, so confirm UI gets correct extension name.
 
   // TODO(rdevlin.cronin): Continue removing std::string errors and replacing
-  // with string16
+  // with base::string16
   std::string utf8_error;
   if (!extension_l10n_util::LocalizeExtension(extension_root_,
                                               final_manifest.get(),
@@ -404,7 +404,7 @@ void SandboxedUnpacker::OnUnpackExtensionSucceeded(
   ReportSuccess(manifest, install_icon);
 }
 
-void SandboxedUnpacker::OnUnpackExtensionFailed(const string16& error) {
+void SandboxedUnpacker::OnUnpackExtensionFailed(const base::string16& error) {
   CHECK(unpacker_io_task_runner_->RunsTasksOnCurrentThread());
   got_response_ = true;
   ReportFailure(
@@ -577,7 +577,7 @@ bool SandboxedUnpacker::ValidateSignature() {
 }
 
 void SandboxedUnpacker::ReportFailure(FailureReason reason,
-                                      const string16& error) {
+                                      const base::string16& error) {
   UMA_HISTOGRAM_ENUMERATION("Extensions.SandboxUnpackFailureReason",
                             reason, NUM_FAILURE_REASONS);
   UMA_HISTOGRAM_TIMES("Extensions.SandboxUnpackFailureTime",
diff --git a/chrome/browser/extensions/sandboxed_unpacker.h b/chrome/browser/extensions/sandboxed_unpacker.h
index 6f4075f..71384fc 100644
--- a/chrome/browser/extensions/sandboxed_unpacker.h
+++ b/chrome/browser/extensions/sandboxed_unpacker.h
@@ -44,7 +44,7 @@ class SandboxedUnpackerClient
                                const base::DictionaryValue* original_manifest,
                                const Extension* extension,
                                const SkBitmap& install_icon) = 0;
-  virtual void OnUnpackFailure(const string16& error) = 0;
+  virtual void OnUnpackFailure(const base::string16& error) = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<SandboxedUnpackerClient>;
@@ -179,9 +179,9 @@ class SandboxedUnpacker : public content::UtilityProcessHostClient {
 
   // IPC message handlers.
   void OnUnpackExtensionSucceeded(const base::DictionaryValue& manifest);
-  void OnUnpackExtensionFailed(const string16& error_message);
+  void OnUnpackExtensionFailed(const base::string16& error_message);
 
-  void ReportFailure(FailureReason reason, const string16& message);
+  void ReportFailure(FailureReason reason, const base::string16& message);
   void ReportSuccess(const base::DictionaryValue& original_manifest,
                      const SkBitmap& install_icon);
 
diff --git a/chrome/browser/extensions/sandboxed_unpacker_unittest.cc b/chrome/browser/extensions/sandboxed_unpacker_unittest.cc
index 5f7e673..3ab39ae 100644
--- a/chrome/browser/extensions/sandboxed_unpacker_unittest.cc
+++ b/chrome/browser/extensions/sandboxed_unpacker_unittest.cc
@@ -47,7 +47,7 @@ class MockSandboxedUnpackerClient : public SandboxedUnpackerClient {
 
   }
 
-  virtual void OnUnpackFailure(const string16& error) OVERRIDE {
+  virtual void OnUnpackFailure(const base::string16& error) OVERRIDE {
     ASSERT_TRUE(false);
   }
 
diff --git a/chrome/browser/extensions/standard_management_policy_provider.cc b/chrome/browser/extensions/standard_management_policy_provider.cc
index ae51540..a9a0d34 100644
--- a/chrome/browser/extensions/standard_management_policy_provider.cc
+++ b/chrome/browser/extensions/standard_management_policy_provider.cc
@@ -33,7 +33,7 @@ std::string
 
 bool StandardManagementPolicyProvider::UserMayLoad(
     const Extension* extension,
-    string16* error) const {
+    base::string16* error) const {
   PrefService* pref_service = prefs_->pref_service();
 
   const base::ListValue* blacklist =
@@ -52,13 +52,13 @@ bool StandardManagementPolicyProvider::UserMayLoad(
 
 bool StandardManagementPolicyProvider::UserMayModifySettings(
     const Extension* extension,
-    string16* error) const {
+    base::string16* error) const {
   return admin_policy::UserMayModifySettings(extension, error);
 }
 
 bool StandardManagementPolicyProvider::MustRemainEnabled(
     const Extension* extension,
-    string16* error) const {
+    base::string16* error) const {
   return admin_policy::MustRemainEnabled(extension, error);
 }
 
diff --git a/chrome/browser/extensions/standard_management_policy_provider.h b/chrome/browser/extensions/standard_management_policy_provider.h
index 5ed53a7..45d4adc 100644
--- a/chrome/browser/extensions/standard_management_policy_provider.h
+++ b/chrome/browser/extensions/standard_management_policy_provider.h
@@ -25,11 +25,11 @@ class StandardManagementPolicyProvider : public ManagementPolicy::Provider {
   // ManagementPolicy::Provider implementation.
   virtual std::string GetDebugPolicyProviderName() const OVERRIDE;
   virtual bool UserMayLoad(const Extension* extension,
-                           string16* error) const OVERRIDE;
+                           base::string16* error) const OVERRIDE;
   virtual bool UserMayModifySettings(const Extension* extension,
-                                     string16* error) const OVERRIDE;
+                                     base::string16* error) const OVERRIDE;
   virtual bool MustRemainEnabled(const Extension* extension,
-                                 string16* error) const OVERRIDE;
+                                 base::string16* error) const OVERRIDE;
 
  private:
   ExtensionPrefs* const prefs_;
diff --git a/chrome/browser/extensions/standard_management_policy_provider_unittest.cc b/chrome/browser/extensions/standard_management_policy_provider_unittest.cc
index 862f95a..f51c27b 100644
--- a/chrome/browser/extensions/standard_management_policy_provider_unittest.cc
+++ b/chrome/browser/extensions/standard_management_policy_provider_unittest.cc
@@ -55,7 +55,7 @@ TEST_F(StandardManagementPolicyProviderTest, RequiredExtension) {
   scoped_refptr<const Extension> extension =
       CreateExtension(Manifest::EXTERNAL_POLICY_DOWNLOAD, true);
 
-  string16 error16;
+  base::string16 error16;
   EXPECT_TRUE(provider_.UserMayLoad(extension.get(), &error16));
   EXPECT_EQ(string16(), error16);
 
@@ -73,7 +73,7 @@ TEST_F(StandardManagementPolicyProviderTest, NotRequiredExtension) {
   scoped_refptr<const Extension> extension =
       CreateExtension(Manifest::INTERNAL, false);
 
-  string16 error16;
+  base::string16 error16;
   EXPECT_TRUE(provider_.UserMayLoad(extension.get(), &error16));
   EXPECT_EQ(string16(), error16);
   EXPECT_TRUE(provider_.UserMayModifySettings(extension.get(), &error16));
diff --git a/chrome/browser/extensions/startup_helper.cc b/chrome/browser/extensions/startup_helper.cc
index 6277e5d..9e87260 100644
--- a/chrome/browser/extensions/startup_helper.cc
+++ b/chrome/browser/extensions/startup_helper.cc
@@ -89,7 +89,7 @@ class ValidateCrxHelper : public SandboxedUnpackerClient {
 
   bool finished() { return finished_; }
   bool success() { return success_; }
-  const string16& error() { return error_; }
+  const base::string16& error() { return error_; }
 
   void Start() {
     BrowserThread::PostTask(BrowserThread::FILE,
@@ -114,7 +114,7 @@ class ValidateCrxHelper : public SandboxedUnpackerClient {
                                        this));
   }
 
-  virtual void OnUnpackFailure(const string16& error) OVERRIDE {
+  virtual void OnUnpackFailure(const base::string16& error) OVERRIDE {
     finished_ = true;
     success_ = false;
     error_ = error;
@@ -161,7 +161,7 @@ class ValidateCrxHelper : public SandboxedUnpackerClient {
   bool success_;
 
   // If the unpacking wasn't successful, this contains an error message.
-  string16 error_;
+  base::string16 error_;
 };
 
 }  // namespace
diff --git a/chrome/browser/extensions/suspicious_extension_bubble_controller.cc b/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
index 421ef84..836da33 100644
--- a/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
+++ b/chrome/browser/extensions/suspicious_extension_bubble_controller.cc
@@ -123,15 +123,15 @@ string16 SuspiciousExtensionBubbleController::GetMessageBody() {
 }
 
 string16 SuspiciousExtensionBubbleController::GetOverflowText(
-    const string16& overflow_count) {
-  string16 overflow_string = l10n_util::GetStringUTF16(
+    const base::string16& overflow_count) {
+  base::string16 overflow_string = l10n_util::GetStringUTF16(
       IDS_EXTENSIONS_SUSPICIOUS_DISABLED_AND_N_MORE);
-  string16 new_string;
+  base::string16 new_string;
 
   // Just before string freeze, we checked in # as a substitution value for
   // this string, whereas we should have used $1. It was discovered too late,
   // so we do the substitution by hand in that case.
-  if (overflow_string.find(ASCIIToUTF16("#")) != string16::npos) {
+  if (overflow_string.find(ASCIIToUTF16("#")) != base::string16::npos) {
     base::ReplaceChars(overflow_string, ASCIIToUTF16("#").c_str(),
                        overflow_count, &new_string);
   } else {
diff --git a/chrome/browser/extensions/suspicious_extension_bubble_controller.h b/chrome/browser/extensions/suspicious_extension_bubble_controller.h
index 0618135..7cd7aa7 100644
--- a/chrome/browser/extensions/suspicious_extension_bubble_controller.h
+++ b/chrome/browser/extensions/suspicious_extension_bubble_controller.h
@@ -36,11 +36,11 @@ class SuspiciousExtensionBubbleController : public ProfileKeyedAPI {
   void Show(SuspiciousExtensionBubble* bubble);
 
   // Text for various UI labels shown in the bubble.
-  string16 GetTitle();
-  string16 GetMessageBody();
-  string16 GetOverflowText(const string16& overflow_count);
-  string16 GetLearnMoreLabel();
-  string16 GetDismissButtonLabel();
+  base::string16 GetTitle();
+  base::string16 GetMessageBody();
+  base::string16 GetOverflowText(const base::string16& overflow_count);
+  base::string16 GetLearnMoreLabel();
+  base::string16 GetDismissButtonLabel();
 
   // Returns a vector of names of suspicious extensions found.
   std::vector<string16> GetSuspiciousExtensionNames();
diff --git a/chrome/browser/extensions/theme_installed_infobar_delegate.h b/chrome/browser/extensions/theme_installed_infobar_delegate.h
index 94727a7..bcc42b4 100644
--- a/chrome/browser/extensions/theme_installed_infobar_delegate.h
+++ b/chrome/browser/extensions/theme_installed_infobar_delegate.h
@@ -46,9 +46,9 @@ class ThemeInstalledInfoBarDelegate : public ConfirmInfoBarDelegate,
   virtual Type GetInfoBarType() const OVERRIDE;
   virtual ThemeInstalledInfoBarDelegate*
       AsThemePreviewInfobarDelegate() OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
   virtual int GetButtons() const OVERRIDE;
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
   virtual bool Cancel() OVERRIDE;
 
   // content::NotificationObserver:
diff --git a/chrome/browser/extensions/unpacked_installer.cc b/chrome/browser/extensions/unpacked_installer.cc
index 52de886..eaad27e 100644
--- a/chrome/browser/extensions/unpacked_installer.cc
+++ b/chrome/browser/extensions/unpacked_installer.cc
@@ -283,7 +283,7 @@ void UnpackedInstaller::ReportExtensionLoadError(const std::string &error) {
 
 void UnpackedInstaller::ConfirmInstall() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  string16 error = installer_.CheckManagementPolicy();
+  base::string16 error = installer_.CheckManagementPolicy();
   if (!error.empty()) {
     ReportExtensionLoadError(UTF16ToUTF8(error));
     return;
diff --git a/chrome/browser/extensions/webstore_installer.cc b/chrome/browser/extensions/webstore_installer.cc
index a2e98d9..b3c28f2 100644
--- a/chrome/browser/extensions/webstore_installer.cc
+++ b/chrome/browser/extensions/webstore_installer.cc
@@ -390,8 +390,9 @@ void WebstoreInstaller::Observe(int type,
         return;
 
       // TODO(rdevlin.cronin): Continue removing std::string errors and
-      // replacing with string16. See crbug.com/71980.
-      const string16* error = content::Details<const string16>(details).ptr();
+      // replacing with base::string16. See crbug.com/71980.
+      const base::string16* error =
+          content::Details<const base::string16>(details).ptr();
       const std::string utf8_error = UTF16ToUTF8(*error);
       if (download_url_ == crx_installer->original_download_url())
         ReportFailure(utf8_error, FAILURE_REASON_OTHER);
diff --git a/chrome/browser/external_extension_browsertest.cc b/chrome/browser/external_extension_browsertest.cc
index 86ee942..37a28e6 100644
--- a/chrome/browser/external_extension_browsertest.cc
+++ b/chrome/browser/external_extension_browsertest.cc
@@ -68,7 +68,7 @@ class SearchProviderTest : public InProcessBrowserTest {
 
   void FinishIsSearchProviderInstalledTest(
       const IsSearchProviderTestData& data) {
-    string16 title = data.tab->GetTitle();
+    base::string16 title = data.tab->GetTitle();
     if (title.empty()) {
       content::TitleWatcher title_watcher(data.tab, ASCIIToUTF16("OK"));
       title_watcher.AlsoWaitForTitle(ASCIIToUTF16("FAIL"));
diff --git a/chrome/browser/geolocation/access_token_store_browsertest.cc b/chrome/browser/geolocation/access_token_store_browsertest.cc
index 399c104..c10e536 100644
--- a/chrome/browser/geolocation/access_token_store_browsertest.cc
+++ b/chrome/browser/geolocation/access_token_store_browsertest.cc
@@ -32,8 +32,8 @@ class GeolocationAccessTokenStoreTest
       : token_to_expect_(NULL), token_to_set_(NULL) {}
 
   void DoTestStepAndWaitForResults(
-      const char* ref_url, const string16* token_to_expect,
-      const string16* token_to_set);
+      const char* ref_url, const base::string16* token_to_expect,
+      const base::string16* token_to_set);
 
   void OnAccessTokenStoresLoaded(
       AccessTokenStore::AccessTokenSet access_token_set,
@@ -41,8 +41,8 @@ class GeolocationAccessTokenStoreTest
 
   scoped_refptr<AccessTokenStore> token_store_;
   GURL ref_url_;
-  const string16* token_to_expect_;
-  const string16* token_to_set_;
+  const base::string16* token_to_expect_;
+  const base::string16* token_to_set_;
 };
 
 void StartTestStepFromClientThread(
@@ -62,8 +62,8 @@ struct TokenLoadClientForTest {
 };
 
 void GeolocationAccessTokenStoreTest::DoTestStepAndWaitForResults(
-    const char* ref_url, const string16* token_to_expect,
-    const string16* token_to_set) {
+    const char* ref_url, const base::string16* token_to_expect,
+    const base::string16* token_to_set) {
   ref_url_ = GURL(ref_url);
   token_to_expect_ = token_to_expect;
   token_to_set_ = token_to_set;
@@ -104,8 +104,8 @@ void GeolocationAccessTokenStoreTest::OnAccessTokenStoresLoaded(
 }
 
 IN_PROC_BROWSER_TEST_F(GeolocationAccessTokenStoreTest, SetAcrossInstances) {
-  const string16 ref_token1 = ASCIIToUTF16("jksdfo90,'s#\"#1*(");
-  const string16 ref_token2 = ASCIIToUTF16("\1\2\3\4\5\6\7\10\11\12=023");
+  const base::string16 ref_token1 = ASCIIToUTF16("jksdfo90,'s#\"#1*(");
+  const base::string16 ref_token2 = ASCIIToUTF16("\1\2\3\4\5\6\7\10\11\12=023");
   ASSERT_TRUE(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   DoTestStepAndWaitForResults(kRefServerUrl1, NULL, &ref_token1);
@@ -122,7 +122,7 @@ IN_PROC_BROWSER_TEST_F(GeolocationAccessTokenStoreTest, SetAcrossInstances) {
 }
 
 IN_PROC_BROWSER_TEST_F(GeolocationAccessTokenStoreTest, OldUrlRemoval) {
-  const string16 ref_token1 = ASCIIToUTF16("jksdfo90,'s#\"#1*(");
+  const base::string16 ref_token1 = ASCIIToUTF16("jksdfo90,'s#\"#1*(");
   ASSERT_TRUE(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Set a token for the old default network provider url.
diff --git a/chrome/browser/geolocation/chrome_access_token_store.cc b/chrome/browser/geolocation/chrome_access_token_store.cc
index 00b9098..1db095d 100644
--- a/chrome/browser/geolocation/chrome_access_token_store.cc
+++ b/chrome/browser/geolocation/chrome_access_token_store.cc
@@ -113,7 +113,7 @@ void ChromeAccessTokenStore::LoadAccessTokens(
 ChromeAccessTokenStore::~ChromeAccessTokenStore() {}
 
 static void SetAccessTokenOnUIThread(const GURL& server_url,
-                                     const string16& token) {
+                                     const base::string16& token) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DictionaryPrefUpdate update(g_browser_process->local_state(),
                               prefs::kGeolocationAccessToken);
@@ -122,8 +122,9 @@ static void SetAccessTokenOnUIThread(const GURL& server_url,
       server_url.spec(), Value::CreateStringValue(token));
 }
 
-void ChromeAccessTokenStore::SaveAccessToken(const GURL& server_url,
-                                             const string16& access_token) {
+void ChromeAccessTokenStore::SaveAccessToken(
+    const GURL& server_url,
+    const base::string16& access_token) {
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(&SetAccessTokenOnUIThread, server_url, access_token));
diff --git a/chrome/browser/geolocation/chrome_access_token_store.h b/chrome/browser/geolocation/chrome_access_token_store.h
index ab7bada..b7b24c0 100644
--- a/chrome/browser/geolocation/chrome_access_token_store.h
+++ b/chrome/browser/geolocation/chrome_access_token_store.h
@@ -25,7 +25,7 @@ class ChromeAccessTokenStore : public content::AccessTokenStore {
 
   // AccessTokenStore
   virtual void SaveAccessToken(
-      const GURL& server_url, const string16& access_token) OVERRIDE;
+      const GURL& server_url, const base::string16& access_token) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeAccessTokenStore);
 };
diff --git a/chrome/browser/geolocation/chrome_geolocation_permission_context_unittest.cc b/chrome/browser/geolocation/chrome_geolocation_permission_context_unittest.cc
index 3c7664a..032d017 100644
--- a/chrome/browser/geolocation/chrome_geolocation_permission_context_unittest.cc
+++ b/chrome/browser/geolocation/chrome_geolocation_permission_context_unittest.cc
@@ -279,7 +279,7 @@ TEST_F(GeolocationPermissionContextTests, GeolocationEnabledDisabled) {
   ConfirmInfoBarDelegate* infobar_delegate_0 = infobar_service()->
       infobar_at(0)->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_0);
-  string16 text_0 = infobar_delegate_0->GetButtonLabel(
+  base::string16 text_0 = infobar_delegate_0->GetButtonLabel(
       ConfirmInfoBarDelegate::BUTTON_OK);
 
   NavigateAndCommit(requesting_frame);
@@ -290,7 +290,7 @@ TEST_F(GeolocationPermissionContextTests, GeolocationEnabledDisabled) {
   ConfirmInfoBarDelegate* infobar_delegate_1 = infobar_service()->
       infobar_at(0)->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_1);
-  string16 text_1 = infobar_delegate_1->GetButtonLabel(
+  base::string16 text_1 = infobar_delegate_1->GetButtonLabel(
       ConfirmInfoBarDelegate::BUTTON_OK);
   EXPECT_NE(text_0, text_1);
 
@@ -355,7 +355,7 @@ TEST_F(GeolocationPermissionContextTests, QueuedPermission) {
   ConfirmInfoBarDelegate* infobar_delegate_0 =
       infobar_0->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_0);
-  string16 text_0 = infobar_delegate_0->GetMessageText();
+  base::string16 text_0 = infobar_delegate_0->GetMessageText();
 
   // Accept the first frame.
   infobar_delegate_0->Accept();
@@ -373,7 +373,7 @@ TEST_F(GeolocationPermissionContextTests, QueuedPermission) {
   ConfirmInfoBarDelegate* infobar_delegate_1 =
       infobar_1->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_1);
-  string16 text_1 = infobar_delegate_1->GetMessageText();
+  base::string16 text_1 = infobar_delegate_1->GetMessageText();
   EXPECT_NE(text_0, text_1);
 
   // Cancel (block) this frame.
@@ -474,7 +474,7 @@ TEST_F(GeolocationPermissionContextTests, CancelGeolocationPermissionRequest) {
   ConfirmInfoBarDelegate* infobar_delegate_0 =
       infobar_0->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_0);
-  string16 text_0 = infobar_delegate_0->GetMessageText();
+  base::string16 text_0 = infobar_delegate_0->GetMessageText();
 
   // Simulate the frame going away, ensure the infobar for this frame
   // is removed and the next pending infobar is created.
@@ -488,7 +488,7 @@ TEST_F(GeolocationPermissionContextTests, CancelGeolocationPermissionRequest) {
   ConfirmInfoBarDelegate* infobar_delegate_1 =
       infobar_1->delegate()->AsConfirmInfoBarDelegate();
   ASSERT_TRUE(infobar_delegate_1);
-  string16 text_1 = infobar_delegate_1->GetMessageText();
+  base::string16 text_1 = infobar_delegate_1->GetMessageText();
   EXPECT_NE(text_0, text_1);
 
   // Allow this frame.
diff --git a/chrome/browser/geolocation/geolocation_browsertest.cc b/chrome/browser/geolocation/geolocation_browsertest.cc
index caa9231..1a6ff11 100644
--- a/chrome/browser/geolocation/geolocation_browsertest.cc
+++ b/chrome/browser/geolocation/geolocation_browsertest.cc
@@ -90,7 +90,7 @@ IFrameLoader::IFrameLoader(Browser* browser, int iframe_id, const GURL& url)
       "window.domAutomationController.send(addIFrame(%d, \"%s\"));",
       iframe_id, url.spec().c_str()));
   web_contents->GetRenderViewHost()->ExecuteJavascriptInWebFrame(
-      string16(), UTF8ToUTF16(script));
+      base::string16(), UTF8ToUTF16(script));
   content::RunMessageLoop();
 
   EXPECT_EQ(base::StringPrintf("\"%d\"", iframe_id), javascript_response_);
diff --git a/chrome/browser/geolocation/geolocation_infobar_delegate.h b/chrome/browser/geolocation/geolocation_infobar_delegate.h
index 342b821..94a0efb 100644
--- a/chrome/browser/geolocation/geolocation_infobar_delegate.h
+++ b/chrome/browser/geolocation/geolocation_infobar_delegate.h
@@ -55,10 +55,10 @@ class GeolocationInfoBarDelegate : public ConfirmInfoBarDelegate {
   virtual Type GetInfoBarType() const OVERRIDE;
   virtual bool ShouldExpireInternal(
       const content::LoadCommittedDetails& details) const OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
   virtual bool Cancel() OVERRIDE;
-  virtual string16 GetLinkText() const OVERRIDE;
+  virtual base::string16 GetLinkText() const OVERRIDE;
   virtual bool LinkClicked(WindowOpenDisposition disposition) OVERRIDE;
 
   PermissionQueueController* controller_;
diff --git a/chrome/browser/geolocation/geolocation_infobar_delegate_android.h b/chrome/browser/geolocation/geolocation_infobar_delegate_android.h
index bca3425..3365656 100644
--- a/chrome/browser/geolocation/geolocation_infobar_delegate_android.h
+++ b/chrome/browser/geolocation/geolocation_infobar_delegate_android.h
@@ -23,7 +23,7 @@ class GeolocationInfoBarDelegateAndroid : public GeolocationInfoBarDelegate {
   virtual ~GeolocationInfoBarDelegateAndroid();
 
   // ConfirmInfoBarDelegate:
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
   virtual bool Accept() OVERRIDE;
 
   scoped_ptr<GoogleLocationSettingsHelper> google_location_settings_helper_;
diff --git a/chrome/browser/google/google_update_win.cc b/chrome/browser/google/google_update_win.cc
index 36358d4..18688cc 100644
--- a/chrome/browser/google/google_update_win.cc
+++ b/chrome/browser/google/google_update_win.cc
@@ -56,7 +56,7 @@ GoogleUpdateErrorCode CanUpdateCurrentChrome(
     return CANNOT_UPGRADE_CHROME_IN_THIS_DIRECTORY;
   }
 
-  string16 app_guid = installer::GetAppGuidForUpdates(
+  base::string16 app_guid = installer::GetAppGuidForUpdates(
       !InstallUtil::IsPerUserInstall(chrome_exe_path.value().c_str()));
   DCHECK(!app_guid.empty());
 
@@ -90,7 +90,7 @@ HRESULT CoCreateInstanceAsAdmin(REFCLSID class_id, REFIID interface_id,
     StringFromGUID2(class_id, class_id_as_string,
                     arraysize(class_id_as_string));
 
-    string16 elevation_moniker_name =
+    base::string16 elevation_moniker_name =
         base::StringPrintf(L"Elevation:Administrator!new:%ls",
                            class_id_as_string);
 
@@ -217,10 +217,10 @@ class GoogleUpdateJobObserver
   GoogleUpdateUpgradeResult result_;
 
   // The version string Google Update found.
-  string16 new_version_;
+  base::string16 new_version_;
 
   // An error message, if any.
-  string16 error_message_;
+  base::string16 error_message_;
 
   // Allows us control the upgrade process to a small degree. After OnComplete
   // has been called, this object can not be used.
@@ -261,7 +261,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
     main_loop->PostTask(
         FROM_HERE,
         base::Bind(&GoogleUpdate::ReportResults, this,
-                   UPGRADE_ERROR, error_code, string16()));
+                   UPGRADE_ERROR, error_code, base::string16()));
     return;
   }
 
@@ -275,7 +275,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
     // Most of the error messages come straight from Google Update. This one is
     // deemed worthy enough to also warrant its own error.
     GoogleUpdateErrorCode error = GOOGLE_UPDATE_JOB_SERVER_CREATION_FAILED;
-    string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
+    base::string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
     ReportFailure(
         hr, error,
         l10n_util::GetStringFUTF16(IDS_ABOUT_BOX_ERROR_UPDATE_CHECK_FAILED,
@@ -308,7 +308,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
 
   if (hr != S_OK) {
     GoogleUpdateErrorCode error = GOOGLE_UPDATE_ONDEMAND_CLASS_NOT_FOUND;
-    string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
+    base::string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
     if (system_level)
       error_code += L" -- system level";
     ReportFailure(hr, error,
@@ -319,7 +319,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
     return;
   }
 
-  string16 app_guid = installer::GetAppGuidForUpdates(system_level);
+  base::string16 app_guid = installer::GetAppGuidForUpdates(system_level);
   DCHECK(!app_guid.empty());
 
   if (!install_if_newer)
@@ -329,7 +329,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
 
   if (hr != S_OK) {
     GoogleUpdateErrorCode error = GOOGLE_UPDATE_ONDEMAND_CLASS_REPORTED_ERROR;
-    string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
+    base::string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
     ReportFailure(hr, error,
                   l10n_util::GetStringFUTF16(
                       IDS_ABOUT_BOX_ERROR_UPDATE_CHECK_FAILED,
@@ -349,7 +349,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
 
   if (hr != S_OK) {
     GoogleUpdateErrorCode error = GOOGLE_UPDATE_GET_RESULT_CALL_FAILED;
-    string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
+    base::string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
     ReportFailure(hr, error,
                   l10n_util::GetStringFUTF16(
                       IDS_ABOUT_BOX_ERROR_UPDATE_CHECK_FAILED,
@@ -359,7 +359,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
   }
 
   if (results == UPGRADE_ERROR) {
-    string16 error_message;
+    base::string16 error_message;
     job_observer->GetErrorMessage(&error_message);
     ReportFailure(hr, GOOGLE_UPDATE_ERROR_UPDATING, error_message, main_loop);
     return;
@@ -368,7 +368,7 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
   hr = job_observer->GetVersionInfo(&version_available_);
   if (hr != S_OK) {
     GoogleUpdateErrorCode error = GOOGLE_UPDATE_GET_VERSION_INFO_FAILED;
-    string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
+    base::string16 error_code = base::StringPrintf(L"%d: 0x%x", error, hr);
     ReportFailure(hr, error,
                   l10n_util::GetStringFUTF16(
                       IDS_ABOUT_BOX_ERROR_UPDATE_CHECK_FAILED,
@@ -380,14 +380,14 @@ void GoogleUpdate::InitiateGoogleUpdateCheck(bool install_if_newer,
   main_loop->PostTask(
       FROM_HERE,
       base::Bind(&GoogleUpdate::ReportResults, this,
-                 results, GOOGLE_UPDATE_NO_ERROR, string16()));
+                 results, GOOGLE_UPDATE_NO_ERROR, base::string16()));
   job_holder = NULL;
   on_demand = NULL;
 }
 
 void GoogleUpdate::ReportResults(GoogleUpdateUpgradeResult results,
                                  GoogleUpdateErrorCode error_code,
-                                 const string16& error_message) {
+                                 const base::string16& error_message) {
   // If there is an error, then error code must not be blank, and vice versa.
   DCHECK(results == UPGRADE_ERROR ? error_code != GOOGLE_UPDATE_NO_ERROR :
                                     error_code == GOOGLE_UPDATE_NO_ERROR);
@@ -399,7 +399,7 @@ void GoogleUpdate::ReportResults(GoogleUpdateUpgradeResult results,
 
 bool GoogleUpdate::ReportFailure(HRESULT hr,
                                  GoogleUpdateErrorCode error_code,
-                                 const string16& error_message,
+                                 const base::string16& error_message,
                                  base::MessageLoop* main_loop) {
   NOTREACHED() << "Communication with Google Update failed: " << hr
                << " error: " << error_code
diff --git a/chrome/browser/google/google_update_win.h b/chrome/browser/google/google_update_win.h
index 06e5fe2..01886eb 100644
--- a/chrome/browser/google/google_update_win.h
+++ b/chrome/browser/google/google_update_win.h
@@ -77,8 +77,8 @@ class GoogleUpdateStatusListener {
   // server config for Chrome) is blank.
   virtual void OnReportResults(GoogleUpdateUpgradeResult results,
                                GoogleUpdateErrorCode error_code,
-                               const string16& error_message,
-                               const string16& version) = 0;
+                               const base::string16& error_message,
+                               const base::string16& version) = 0;
 };
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -115,7 +115,7 @@ class GoogleUpdate : public base::RefCountedThreadSafe<GoogleUpdate> {
   // listener.
   // Note, after this function completes, this object will have deleted itself.
   bool ReportFailure(HRESULT hr, GoogleUpdateErrorCode error_code,
-                     const string16& error_message,
+                     const base::string16& error_message,
                      base::MessageLoop* main_loop);
 
   // The update check needs to run on another thread than the main thread, and
@@ -132,11 +132,11 @@ class GoogleUpdate : public base::RefCountedThreadSafe<GoogleUpdate> {
   // Note, after this function completes, this object will have deleted itself.
   void ReportResults(GoogleUpdateUpgradeResult results,
                      GoogleUpdateErrorCode error_code,
-                     const string16& error_message);
+                     const base::string16& error_message);
 
   // Which version string Google Update found (if a new one was available).
   // Otherwise, this will be blank.
-  string16 version_available_;
+  base::string16 version_available_;
 
   // The listener who is interested in finding out the result of the operation.
   GoogleUpdateStatusListener* listener_;
diff --git a/chrome/browser/google/google_url_tracker.cc b/chrome/browser/google/google_url_tracker.cc
index c6160af..81cb919 100644
--- a/chrome/browser/google/google_url_tracker.cc
+++ b/chrome/browser/google/google_url_tracker.cc
@@ -155,7 +155,7 @@ void GoogleURLTracker::OnURLFetchComplete(const net::URLFetcher* source) {
     return;
   }
 
-  string16 fetched_host(net::StripWWWFromHost(fetched_google_url_));
+  base::string16 fetched_host(net::StripWWWFromHost(fetched_google_url_));
   if (fetched_google_url_ == google_url_) {
     // Either the user has continually been on this URL, or we prompted for a
     // different URL but have now changed back before they responded to any of
diff --git a/chrome/browser/google/google_url_tracker_infobar_delegate.h b/chrome/browser/google/google_url_tracker_infobar_delegate.h
index 36b482a..cbeab03 100644
--- a/chrome/browser/google/google_url_tracker_infobar_delegate.h
+++ b/chrome/browser/google/google_url_tracker_infobar_delegate.h
@@ -41,9 +41,9 @@ class GoogleURLTrackerInfoBarDelegate : public ConfirmInfoBarDelegate {
 
  private:
   // ConfirmInfoBarDelegate:
-  virtual string16 GetMessageText() const OVERRIDE;
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
-  virtual string16 GetLinkText() const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetLinkText() const OVERRIDE;
   virtual bool LinkClicked(WindowOpenDisposition disposition) OVERRIDE;
   virtual bool ShouldExpireInternal(
       const content::LoadCommittedDetails& details) const OVERRIDE;
diff --git a/chrome/browser/google/google_util.cc b/chrome/browser/google/google_util.cc
index 99e4b7a..fe4c9df 100644
--- a/chrome/browser/google/google_util.cc
+++ b/chrome/browser/google/google_util.cc
@@ -112,7 +112,7 @@ bool GetBrand(std::string* brand) {
     return true;
   }
 
-  string16 brand16;
+  base::string16 brand16;
   bool ret = GoogleUpdateSettings::GetBrand(&brand16);
   if (ret)
     brand->assign(WideToASCII(brand16));
@@ -120,7 +120,7 @@ bool GetBrand(std::string* brand) {
 }
 
 bool GetReactivationBrand(std::string* brand) {
-  string16 brand16;
+  base::string16 brand16;
   bool ret = GoogleUpdateSettings::GetReactivationBrand(&brand16);
   if (ret)
     brand->assign(WideToASCII(brand16));
diff --git a/chrome/browser/history/android/android_cache_database.cc b/chrome/browser/history/android/android_cache_database.cc
index 1fdd981..5df7951 100644
--- a/chrome/browser/history/android/android_cache_database.cc
+++ b/chrome/browser/history/android/android_cache_database.cc
@@ -108,7 +108,7 @@ bool AndroidCacheDatabase::SetFaviconID(URLID url_id,
 }
 
 SearchTermID AndroidCacheDatabase::AddSearchTerm(
-    const string16& term,
+    const base::string16& term,
     const base::Time& last_visit_time) {
   sql::Statement statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
       "INSERT INTO android_cache_db.search_terms (search, "
@@ -139,7 +139,7 @@ bool AndroidCacheDatabase::UpdateSearchTerm(SearchTermID id,
   return statement.Run();
 }
 
-SearchTermID AndroidCacheDatabase::GetSearchTerm(const string16& term,
+SearchTermID AndroidCacheDatabase::GetSearchTerm(const base::string16& term,
                                                  SearchTermRow* row) {
   sql::Statement statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
       "SELECT _id, search, date "
diff --git a/chrome/browser/history/android/android_cache_database.h b/chrome/browser/history/android/android_cache_database.h
index 4f4dd19..314e0d1 100644
--- a/chrome/browser/history/android/android_cache_database.h
+++ b/chrome/browser/history/android/android_cache_database.h
@@ -49,7 +49,7 @@ class AndroidCacheDatabase {
   // Add a row in the search_term table with the given |term| and
   // |last_visit_time|. Return the new row's id on success, otherwise 0 is
   // returned.
-  SearchTermID AddSearchTerm(const string16& term,
+  SearchTermID AddSearchTerm(const base::string16& term,
                              const base::Time& last_visit_time);
 
   // Updates the |id|'s row with the given |row|; returns true on success.
@@ -58,7 +58,7 @@ class AndroidCacheDatabase {
   // Get SearchTermRow of the given |term|; return the row id on success.
   // otherwise 0 is returned.
   // The found row is return in |row| if it is not NULL.
-  SearchTermID GetSearchTerm(const string16& term, SearchTermRow* row);
+  SearchTermID GetSearchTerm(const base::string16& term, SearchTermRow* row);
 
   // Delete the search terms which don't exist in keyword_search_terms table.
   bool DeleteUnusedSearchTerms();
diff --git a/chrome/browser/history/android/android_cache_database_unittest.cc b/chrome/browser/history/android/android_cache_database_unittest.cc
index e586874..e56e3e9 100644
--- a/chrome/browser/history/android/android_cache_database_unittest.cc
+++ b/chrome/browser/history/android/android_cache_database_unittest.cc
@@ -73,7 +73,7 @@ TEST_F(AndroidCacheDatabaseTest, InitAndroidCacheDatabase) {
 TEST_F(AndroidCacheDatabaseTest, SearchTermsTable) {
   // Test AddSearchTerm.
   Time search_time1 = Time::Now() - TimeDelta::FromDays(1);
-  string16 search_term1(UTF8ToUTF16("search term 1"));
+  base::string16 search_term1(UTF8ToUTF16("search term 1"));
   SearchTermID id1 = history_db_.AddSearchTerm(search_term1, search_time1);
   ASSERT_TRUE(id1);
   SearchTermRow row1;
@@ -95,7 +95,7 @@ TEST_F(AndroidCacheDatabaseTest, SearchTermsTable) {
   EXPECT_EQ(id1, row1.id);
 
   Time search_time2 = Time::Now() - TimeDelta::FromHours(1);
-  string16 search_term2(UTF8ToUTF16("search term 2"));
+  base::string16 search_term2(UTF8ToUTF16("search term 2"));
   SearchTermID id2 = history_db_.AddSearchTerm(search_term2, search_time2);
   ASSERT_TRUE(id2);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(1, 1, search_term2));
diff --git a/chrome/browser/history/android/android_history_types.h b/chrome/browser/history/android/android_history_types.h
index 843f465..8bef571e 100644
--- a/chrome/browser/history/android/android_history_types.h
+++ b/chrome/browser/history/android/android_history_types.h
@@ -72,11 +72,11 @@ class HistoryAndBookmarkRow {
   }
 
   // The title of page.
-  void set_title(const string16& title) {
+  void set_title(const base::string16& title) {
     set_value_explicitly(TITLE);
     title_ = title;
   }
-  const string16& title() const {
+  const base::string16& title() const {
     return title_;
   }
 
@@ -169,7 +169,7 @@ class HistoryAndBookmarkRow {
   AndroidURLID id_;
   GURL url_;
   std::string raw_url_;
-  string16 title_;
+  base::string16 title_;
   base::Time created_;
   base::Time last_visit_time_;
   scoped_refptr<base::RefCountedMemory> favicon_;
@@ -219,10 +219,10 @@ class SearchRow {
     id_ = id;
   }
 
-  const string16& search_term() const {
+  const base::string16& search_term() const {
     return search_term_;
   }
-  void set_search_term(const string16& search_term) {
+  void set_search_term(const base::string16& search_term) {
     set_value_explicitly(SearchRow::SEARCH_TERM);
     search_term_ = search_term;
   }
@@ -262,7 +262,7 @@ class SearchRow {
   }
 
   SearchTermID id_;
-  string16 search_term_;
+  base::string16 search_term_;
   base::Time search_time_;
   GURL url_;
   TemplateURLID template_url_id_;
@@ -294,7 +294,7 @@ struct SearchTermRow {
   // The unique id of the row.
   SearchTermID id;
   // The keyword.
-  string16 term;
+  base::string16 term;
   // The last visit time.
   base::Time last_visit_time;
 };
diff --git a/chrome/browser/history/android/android_provider_backend.cc b/chrome/browser/history/android/android_provider_backend.cc
index ff69a0e..599e9dc 100644
--- a/chrome/browser/history/android/android_provider_backend.cc
+++ b/chrome/browser/history/android/android_provider_backend.cc
@@ -827,7 +827,7 @@ bool AndroidProviderBackend::UpdateSearchTermTable() {
   sql::Statement statement(db_->GetCachedStatement(SQL_FROM_HERE,
                                                    kSearchTermUpdateClause));
   while (statement.Step()) {
-    string16 term = statement.ColumnString16(0);
+    base::string16 term = statement.ColumnString16(0);
     Time last_visit_time = Time::FromInternalValue(statement.ColumnInt64(1));
     SearchTermRow search_term_row;
     if (history_db_->GetSearchTerm(term, &search_term_row)) {
diff --git a/chrome/browser/history/android/android_provider_backend_unittest.cc b/chrome/browser/history/android/android_provider_backend_unittest.cc
index 0d3d1c7..16145f1 100644
--- a/chrome/browser/history/android/android_provider_backend_unittest.cc
+++ b/chrome/browser/history/android/android_provider_backend_unittest.cc
@@ -149,7 +149,7 @@ class AndroidProviderBackendTest : public testing::Test {
   void AddBookmark(const GURL& url) {
     const BookmarkNode* mobile_node = bookmark_model_->mobile_node();
     ASSERT_TRUE(mobile_node);
-    ASSERT_TRUE(bookmark_model_->AddURL(mobile_node, 0, string16(), url));
+    ASSERT_TRUE(bookmark_model_->AddURL(mobile_node, 0, base::string16(), url));
   }
 
   bool GetAndroidURLsRows(std::vector<AndroidURLRow>* rows,
@@ -227,7 +227,7 @@ TEST_F(AndroidProviderBackendTest, UpdateTables) {
 
   // Add a bookmark which is not in the history.
   GURL url3("http://www.bookmark.com");
-  string16 title3(UTF8ToUTF16("bookmark"));
+  base::string16 title3(UTF8ToUTF16("bookmark"));
   ASSERT_TRUE(bookmark_model_->AddURL(bookmark_model_->bookmark_bar_node(), 0,
                                       title3, url3));
   // Only use the HistoryBackend to generate the test data.
@@ -354,7 +354,7 @@ TEST_F(AndroidProviderBackendTest, UpdateTables) {
 TEST_F(AndroidProviderBackendTest, QueryHistoryAndBookmarks) {
   GURL url1("http://www.cnn.com");
   URLID url_id1 = 0;
-  const string16 title1(UTF8ToUTF16("cnn"));
+  const base::string16 title1(UTF8ToUTF16("cnn"));
   std::vector<VisitInfo> visits1;
   Time last_visited1 = Time::Now() - TimeDelta::FromDays(1);
   Time created1 = last_visited1 - TimeDelta::FromDays(20);
@@ -366,7 +366,7 @@ TEST_F(AndroidProviderBackendTest, QueryHistoryAndBookmarks) {
   GURL url2("http://www.example.com");
   URLID url_id2 = 0;
   std::vector<VisitInfo> visits2;
-  const string16 title2(UTF8ToUTF16("example"));
+  const base::string16 title2(UTF8ToUTF16("example"));
   Time last_visited2 = Time::Now();
   Time created2 = last_visited2 - TimeDelta::FromDays(10);
   visits2.push_back(VisitInfo(created2, content::PAGE_TRANSITION_LINK));
@@ -1195,7 +1195,7 @@ TEST_F(AndroidProviderBackendTest, UpdateSearchTermTable) {
   row1.set_last_visit_time(Time::Now() - TimeDelta::FromDays(1));
   row1.set_title(UTF8ToUTF16("cnn"));
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row1));
-  string16 term = UTF8ToUTF16("Search term 1");
+  base::string16 term = UTF8ToUTF16("Search term 1");
   URLID url_id = history_db_.GetRowForURL(row1.url(), NULL);
   ASSERT_TRUE(url_id);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id, 1, term));
@@ -1216,7 +1216,7 @@ TEST_F(AndroidProviderBackendTest, UpdateSearchTermTable) {
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row2));
   url_id = history_db_.GetRowForURL(row2.url(), NULL);
   ASSERT_TRUE(url_id);
-  string16 term2 = UTF8ToUTF16("Search term 2");
+  base::string16 term2 = UTF8ToUTF16("Search term 2");
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id, 1, term2));
   ASSERT_TRUE(backend->UpdateSearchTermTable());
   SearchTermID search_id1 = history_db_.GetSearchTerm(term,
@@ -1273,7 +1273,7 @@ TEST_F(AndroidProviderBackendTest, QuerySearchTerms) {
   row1.set_last_visit_time(Time::Now() - TimeDelta::FromDays(1));
   row1.set_title(UTF8ToUTF16("cnn"));
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row1));
-  string16 term = UTF8ToUTF16("Search term 1");
+  base::string16 term = UTF8ToUTF16("Search term 1");
   URLID url_id = history_db_.GetRowForURL(row1.url(), NULL);
   ASSERT_TRUE(url_id);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id, 1, term));
@@ -1306,7 +1306,7 @@ TEST_F(AndroidProviderBackendTest, UpdateSearchTerms) {
   row1.set_last_visit_time(Time::Now() - TimeDelta::FromDays(1));
   row1.set_title(UTF8ToUTF16("cnn"));
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row1));
-  string16 term = UTF8ToUTF16("Search term 1");
+  base::string16 term = UTF8ToUTF16("Search term 1");
   URLID url_id = history_db_.GetRowForURL(row1.url(), NULL);
   ASSERT_TRUE(url_id);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id, 1, term));
@@ -1327,7 +1327,7 @@ TEST_F(AndroidProviderBackendTest, UpdateSearchTerms) {
   EXPECT_FALSE(statement->statement()->Step());
 
   // Update the search term and time.
-  string16 update_term = UTF8ToUTF16("Update search term");
+  base::string16 update_term = UTF8ToUTF16("Update search term");
   args.clear();
   args.push_back(term);
   SearchRow search_row;
@@ -1410,7 +1410,7 @@ TEST_F(AndroidProviderBackendTest, DeleteSearchTerms) {
   row1.set_last_visit_time(Time::Now() - TimeDelta::FromDays(1));
   row1.set_title(UTF8ToUTF16("cnn"));
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row1));
-  string16 term = UTF8ToUTF16("Search term 1");
+  base::string16 term = UTF8ToUTF16("Search term 1");
   URLID url_id = history_db_.GetRowForURL(row1.url(), NULL);
   ASSERT_TRUE(url_id);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id, 1, term));
@@ -1437,7 +1437,7 @@ TEST_F(AndroidProviderBackendTest, DeleteSearchTerms) {
   row2.set_last_visit_time(Time::Now() - TimeDelta::FromDays(1));
   row2.set_title(UTF8ToUTF16("google"));
   ASSERT_TRUE(backend->InsertHistoryAndBookmark(row2));
-  string16 term2 = UTF8ToUTF16("Search term 2");
+  base::string16 term2 = UTF8ToUTF16("Search term 2");
   URLID url_id2 = history_db_.GetRowForURL(row2.url(), NULL);
   ASSERT_TRUE(url_id2);
   ASSERT_TRUE(history_db_.SetKeywordSearchTermsForURL(url_id2, 1, term2));
@@ -1751,7 +1751,7 @@ TEST_F(AndroidProviderBackendTest, AndroidCTSComplianceFolderColumnExists) {
 TEST_F(AndroidProviderBackendTest, QueryWithoutThumbnailDB) {
   GURL url1("http://www.cnn.com");
   URLID url_id1 = 0;
-  const string16 title1(UTF8ToUTF16("cnn"));
+  const base::string16 title1(UTF8ToUTF16("cnn"));
   std::vector<VisitInfo> visits1;
   Time last_visited1 = Time::Now() - TimeDelta::FromDays(1);
   Time created1 = last_visited1 - TimeDelta::FromDays(20);
@@ -1763,7 +1763,7 @@ TEST_F(AndroidProviderBackendTest, QueryWithoutThumbnailDB) {
   GURL url2("http://www.example.com");
   URLID url_id2 = 0;
   std::vector<VisitInfo> visits2;
-  const string16 title2(UTF8ToUTF16("example"));
+  const base::string16 title2(UTF8ToUTF16("example"));
   Time last_visited2 = Time::Now();
   Time created2 = last_visited2 - TimeDelta::FromDays(10);
   visits2.push_back(VisitInfo(created2, content::PAGE_TRANSITION_LINK));
diff --git a/chrome/browser/history/android/bookmark_model_sql_handler.cc b/chrome/browser/history/android/bookmark_model_sql_handler.cc
index 98e2460..446d2af 100644
--- a/chrome/browser/history/android/bookmark_model_sql_handler.cc
+++ b/chrome/browser/history/android/bookmark_model_sql_handler.cc
@@ -31,7 +31,7 @@ BookmarkModelSQLHandler::Task::Task() {
 
 void BookmarkModelSQLHandler::Task::AddBookmarkToMobileFolder(
     const GURL& url,
-    const string16& title) {
+    const base::string16& title) {
   BookmarkModel* bookmark_model = GetBookmarkModel();
   if (!bookmark_model)
     return;
@@ -41,7 +41,7 @@ void BookmarkModelSQLHandler::Task::AddBookmarkToMobileFolder(
 }
 
 void BookmarkModelSQLHandler::Task::AddBookmark(const GURL& url,
-                                                const string16& title,
+                                                const base::string16& title,
                                                 int64 parent_id) {
   BookmarkModel* bookmark_model = GetBookmarkModel();
   if (!bookmark_model)
@@ -64,8 +64,9 @@ void BookmarkModelSQLHandler::Task::RemoveBookmark(const GURL& url) {
   }
 }
 
-void BookmarkModelSQLHandler::Task::UpdateBookmarkTitle(const GURL& url,
-                                                        const string16&title) {
+void BookmarkModelSQLHandler::Task::UpdateBookmarkTitle(
+    const GURL& url,
+    const base::string16& title) {
   BookmarkModel* bookmark_model = GetBookmarkModel();
   if (!bookmark_model)
     return;
@@ -170,4 +171,4 @@ bool BookmarkModelSQLHandler::Insert(HistoryAndBookmarkRow* row) {
   return true;
 }
 
-}  // namespace history.
+}  // namespace history
diff --git a/chrome/browser/history/android/bookmark_model_sql_handler.h b/chrome/browser/history/android/bookmark_model_sql_handler.h
index 672cf4d..f2a5ef7 100644
--- a/chrome/browser/history/android/bookmark_model_sql_handler.h
+++ b/chrome/browser/history/android/bookmark_model_sql_handler.h
@@ -42,16 +42,20 @@ class BookmarkModelSQLHandler : public SQLHandler {
     Task();
 
     // Add the a bookmark with the given |url| to mobile folder.
-    void AddBookmarkToMobileFolder(const GURL& url, const string16& title);
+    void AddBookmarkToMobileFolder(const GURL& url,
+                                   const base::string16& title);
 
     // Adds a bookmark with the given |url|, |title| and |parent_id|.
-    void AddBookmark(const GURL& url, const string16& title, int64 parent_id);
+    void AddBookmark(const GURL& url,
+                     const base::string16& title,
+                     int64 parent_id);
 
     // Removes the bookmark with the given |url|.
     void RemoveBookmark(const GURL& url);
 
     // Updates the given bookmark's title.
-    void UpdateBookmarkTitle(const GURL& url, const string16&title);
+    void UpdateBookmarkTitle(const GURL& url,
+                             const base::string16& title);
 
    private:
     friend class base::RefCountedThreadSafe<Task>;
diff --git a/chrome/browser/history/android/sqlite_cursor.cc b/chrome/browser/history/android/sqlite_cursor.cc
index 36cc882..53e9ef5 100644
--- a/chrome/browser/history/android/sqlite_cursor.cc
+++ b/chrome/browser/history/android/sqlite_cursor.cc
@@ -80,7 +80,7 @@ ScopedJavaLocalRef<jobjectArray> SQLiteCursor::GetColumnNames(JNIEnv* env,
 ScopedJavaLocalRef<jstring> SQLiteCursor::GetString(JNIEnv* env,
                                                     jobject obj,
                                                     jint column) {
-  string16 value = statement_->statement()->ColumnString16(column);
+  base::string16 value = statement_->statement()->ColumnString16(column);
   return ScopedJavaLocalRef<jstring>(env,
       env->NewString(value.data(), value.size()));
 }
diff --git a/chrome/browser/history/expire_history_backend_unittest.cc b/chrome/browser/history/expire_history_backend_unittest.cc
index d91409b..105bc7d 100644
--- a/chrome/browser/history/expire_history_backend_unittest.cc
+++ b/chrome/browser/history/expire_history_backend_unittest.cc
@@ -87,7 +87,7 @@ class ExpireHistoryTest : public testing::Test,
 
   void StarURL(const GURL& url) {
     bookmark_model_.AddURL(
-        bookmark_model_.bookmark_bar_node(), 0, string16(), url);
+        bookmark_model_.bookmark_bar_node(), 0, base::string16(), url);
   }
 
   static bool IsStringInFile(const base::FilePath& filename, const char* str);
diff --git a/chrome/browser/history/history_backend.cc b/chrome/browser/history/history_backend.cc
index be5a171..1afbeaa 100644
--- a/chrome/browser/history/history_backend.cc
+++ b/chrome/browser/history/history_backend.cc
@@ -873,7 +873,8 @@ bool HistoryBackend::IsExpiredVisitTime(const base::Time& time) {
   return time < expirer_.GetCurrentArchiveTime();
 }
 
-void HistoryBackend::SetPageTitle(const GURL& url, const string16& title) {
+void HistoryBackend::SetPageTitle(const GURL& url,
+                                  const base::string16& title) {
   if (!db_)
     return;
 
@@ -919,7 +920,7 @@ void HistoryBackend::SetPageTitle(const GURL& url, const string16& title) {
 }
 
 void HistoryBackend::AddPageNoVisitForBookmark(const GURL& url,
-                                               const string16& title) {
+                                               const base::string16& title) {
   if (!db_)
     return;
 
@@ -1129,7 +1130,7 @@ void HistoryBackend::QuerySegmentDuration(
 
 void HistoryBackend::SetKeywordSearchTermsForURL(const GURL& url,
                                                  TemplateURLID keyword_id,
-                                                 const string16& term) {
+                                                 const base::string16& term) {
   if (!db_)
     return;
 
@@ -1162,7 +1163,7 @@ void HistoryBackend::DeleteAllSearchTermsForKeyword(
 void HistoryBackend::GetMostRecentKeywordSearchTerms(
     scoped_refptr<GetMostRecentKeywordSearchTermsRequest> request,
     TemplateURLID keyword_id,
-    const string16& prefix,
+    const base::string16& prefix,
     int max_count) {
   if (request->canceled())
     return;
@@ -1253,7 +1254,7 @@ void HistoryBackend::RemoveDownloads(const std::set<uint32>& ids) {
 }
 
 void HistoryBackend::QueryHistory(scoped_refptr<QueryHistoryRequest> request,
-                                  const string16& text_query,
+                                  const base::string16& text_query,
                                   const QueryOptions& options) {
   if (request->canceled())
     return;
@@ -1348,7 +1349,7 @@ void HistoryBackend::QueryHistoryBasic(URLDatabase* url_db,
 // Text-based querying of history.
 void HistoryBackend::QueryHistoryText(URLDatabase* url_db,
                                       VisitDatabase* visit_db,
-                                      const string16& text_query,
+                                      const base::string16& text_query,
                                       const QueryOptions& options,
                                       QueryResults* result) {
   URLRows text_matches;
diff --git a/chrome/browser/history/history_backend.h b/chrome/browser/history/history_backend.h
index a4971b2..6139966 100644
--- a/chrome/browser/history/history_backend.h
+++ b/chrome/browser/history/history_backend.h
@@ -143,8 +143,8 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 
   // |request.time| must be unique with high probability.
   void AddPage(const HistoryAddPageArgs& request);
-  virtual void SetPageTitle(const GURL& url, const string16& title);
-  void AddPageNoVisitForBookmark(const GURL& url, const string16& title);
+  virtual void SetPageTitle(const GURL& url, const base::string16& title);
+  void AddPageNoVisitForBookmark(const GURL& url, const base::string16& title);
 
   // Updates the database backend with a page's ending time stamp information.
   // The page can be identified by the combination of the pointer to
@@ -172,7 +172,7 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
                 const GURL& url,
                 bool want_visits);
   void QueryHistory(scoped_refptr<QueryHistoryRequest> request,
-                    const string16& text_query,
+                    const base::string16& text_query,
                     const QueryOptions& options);
   void QueryRedirectsFrom(scoped_refptr<QueryRedirectsRequest> request,
                           const GURL& url);
@@ -308,14 +308,14 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 
   void SetKeywordSearchTermsForURL(const GURL& url,
                                    TemplateURLID keyword_id,
-                                   const string16& term);
+                                   const base::string16& term);
 
   void DeleteAllSearchTermsForKeyword(TemplateURLID keyword_id);
 
   void GetMostRecentKeywordSearchTerms(
       scoped_refptr<GetMostRecentKeywordSearchTermsRequest> request,
       TemplateURLID keyword_id,
-      const string16& prefix,
+      const base::string16& prefix,
       int max_count);
 
   void DeleteKeywordSearchTermForURL(const GURL& url);
@@ -620,7 +620,7 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
                          const QueryOptions& options, QueryResults* result);
   void QueryHistoryText(URLDatabase* url_db,
                         VisitDatabase* visit_db,
-                        const string16& text_query,
+                        const base::string16& text_query,
                         const QueryOptions& options,
                         QueryResults* result);
 
diff --git a/chrome/browser/history/history_backend_unittest.cc b/chrome/browser/history/history_backend_unittest.cc
index 5d01cf1..fe772a8 100644
--- a/chrome/browser/history/history_backend_unittest.cc
+++ b/chrome/browser/history/history_backend_unittest.cc
@@ -504,7 +504,7 @@ TEST_F(HistoryBackendTest, DeleteAll) {
 
   // Star row1.
   bookmark_model_.AddURL(
-      bookmark_model_.bookmark_bar_node(), 0, string16(), row1.url());
+      bookmark_model_.bookmark_bar_node(), 0, base::string16(), row1.url());
 
   // Now finally clear all history.
   backend_->DeleteAllHistory();
@@ -654,8 +654,10 @@ TEST_F(HistoryBackendTest, URLsNoLongerBookmarked) {
   URLID row2_id = backend_->db_->GetRowForURL(row2.url(), NULL);
 
   // Star the two URLs.
-  bookmark_utils::AddIfNotBookmarked(&bookmark_model_, row1.url(), string16());
-  bookmark_utils::AddIfNotBookmarked(&bookmark_model_, row2.url(), string16());
+  bookmark_utils::AddIfNotBookmarked(&bookmark_model_, row1.url(),
+                                     base::string16());
+  bookmark_utils::AddIfNotBookmarked(&bookmark_model_, row2.url(),
+                                     base::string16());
 
   // Delete url 2. Because url 2 is starred this won't delete the URL, only
   // the visits.
@@ -862,8 +864,8 @@ TEST_F(HistoryBackendTest, ImportedFaviconsTest) {
   EXPECT_TRUE(backend_->db_->GetRowForURL(url3, &url_row3) == 0);
 
   // If the URL is bookmarked, it should get added to history with 0 visits.
-  bookmark_model_.AddURL(bookmark_model_.bookmark_bar_node(), 0, string16(),
-                         url3);
+  bookmark_model_.AddURL(bookmark_model_.bookmark_bar_node(), 0,
+                         base::string16(), url3);
   backend_->SetImportedFavicons(favicons);
   EXPECT_FALSE(backend_->db_->GetRowForURL(url3, &url_row3) == 0);
   EXPECT_TRUE(url_row3.visit_count() == 0);
@@ -2612,7 +2614,7 @@ TEST_F(HistoryBackendTest, AddPageNoVisitForBookmark) {
   ASSERT_TRUE(backend_.get());
 
   GURL url("http://www.google.com");
-  string16 title(UTF8ToUTF16("Bookmark title"));
+  base::string16 title(UTF8ToUTF16("Bookmark title"));
   backend_->AddPageNoVisitForBookmark(url, title);
 
   URLRow row;
@@ -2622,7 +2624,7 @@ TEST_F(HistoryBackendTest, AddPageNoVisitForBookmark) {
   EXPECT_EQ(0, row.visit_count());
 
   backend_->DeleteURL(url);
-  backend_->AddPageNoVisitForBookmark(url, string16());
+  backend_->AddPageNoVisitForBookmark(url, base::string16());
   backend_->GetURL(url, &row);
   EXPECT_EQ(url, row.url());
   EXPECT_EQ(UTF8ToUTF16(url.spec()), row.title());
diff --git a/chrome/browser/history/history_browsertest.cc b/chrome/browser/history/history_browsertest.cc
index e2f8f2a..5f2a050 100644
--- a/chrome/browser/history/history_browsertest.cc
+++ b/chrome/browser/history/history_browsertest.cc
@@ -101,7 +101,7 @@ class HistoryBrowserTest : public InProcessBrowserTest {
   }
 
   void LoadAndWaitForURL(const GURL& url) {
-    string16 expected_title(ASCIIToUTF16("OK"));
+    base::string16 expected_title(ASCIIToUTF16("OK"));
     content::TitleWatcher title_watcher(
         browser()->tab_strip_model()->GetActiveWebContents(), expected_title);
     title_watcher.AlsoWaitForTitle(ASCIIToUTF16("FAIL"));
@@ -466,7 +466,7 @@ IN_PROC_BROWSER_TEST_F(HistoryBrowserTest, SubmitFormAddsTargetPage) {
 
   content::WebContents* web_contents =
       browser()->tab_strip_model()->GetActiveWebContents();
-  string16 expected_title(ASCIIToUTF16("Target Page"));
+  base::string16 expected_title(ASCIIToUTF16("Target Page"));
   content::TitleWatcher title_watcher(
       browser()->tab_strip_model()->GetActiveWebContents(), expected_title);
   ASSERT_TRUE(content::ExecuteScript(
@@ -488,7 +488,7 @@ IN_PROC_BROWSER_TEST_F(HistoryBrowserTest, OneHistoryTabPerWindow) {
   // 'Loading...' for a brief time while the history page loads.
   content::WebContents* web_contents =
       browser()->tab_strip_model()->GetActiveWebContents();
-  string16 expected_title(ASCIIToUTF16("History"));
+  base::string16 expected_title(ASCIIToUTF16("History"));
   content::TitleWatcher title_watcher(web_contents, expected_title);
   chrome::ExecuteCommand(browser(), IDC_SHOW_HISTORY);
   EXPECT_EQ(expected_title, title_watcher.WaitAndGetTitle());
diff --git a/chrome/browser/history/history_notifications.cc b/chrome/browser/history/history_notifications.cc
index 477ffc9..d0d9be6 100644
--- a/chrome/browser/history/history_notifications.cc
+++ b/chrome/browser/history/history_notifications.cc
@@ -25,7 +25,7 @@ URLsDeletedDetails::~URLsDeletedDetails() {}
 KeywordSearchUpdatedDetails::KeywordSearchUpdatedDetails(
     const GURL& url,
     TemplateURLID keyword_id,
-    const string16& term)
+    const base::string16& term)
     : url(url),
       keyword_id(keyword_id),
       term(term) {
diff --git a/chrome/browser/history/history_notifications.h b/chrome/browser/history/history_notifications.h
index ad8ae31..29de877 100644
--- a/chrome/browser/history/history_notifications.h
+++ b/chrome/browser/history/history_notifications.h
@@ -65,12 +65,12 @@ struct URLsDeletedDetails : public HistoryDetails {
 struct KeywordSearchUpdatedDetails : public HistoryDetails {
   KeywordSearchUpdatedDetails(const GURL& url,
                               TemplateURLID keyword_id,
-                              const string16& term);
+                              const base::string16& term);
   virtual ~KeywordSearchUpdatedDetails();
 
   GURL url;
   TemplateURLID keyword_id;
-  string16 term;
+  base::string16 term;
 };
 
 // Details for HISTORY_KEYWORD_SEARCH_TERM_DELETED.
diff --git a/chrome/browser/history/history_service.cc b/chrome/browser/history/history_service.cc
index f1bdf22..c615675 100644
--- a/chrome/browser/history/history_service.cc
+++ b/chrome/browser/history/history_service.cc
@@ -376,7 +376,7 @@ void HistoryService::Shutdown() {
 
 void HistoryService::SetKeywordSearchTermsForURL(const GURL& url,
                                                  TemplateURLID keyword_id,
-                                                 const string16& term) {
+                                                 const base::string16& term) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ScheduleAndForget(PRIORITY_UI,
                     &HistoryBackend::SetKeywordSearchTermsForURL,
@@ -393,7 +393,7 @@ void HistoryService::DeleteAllSearchTermsForKeyword(
 
 HistoryService::Handle HistoryService::GetMostRecentKeywordSearchTerms(
     TemplateURLID keyword_id,
-    const string16& prefix,
+    const base::string16& prefix,
     int max_count,
     CancelableRequestConsumerBase* consumer,
     const GetMostRecentKeywordSearchTermsCallback& callback) {
@@ -524,7 +524,7 @@ void HistoryService::AddPage(const history::HistoryAddPageArgs& add_page_args) {
 }
 
 void HistoryService::AddPageNoVisitForBookmark(const GURL& url,
-                                               const string16& title) {
+                                               const base::string16& title) {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!CanAddURL(url))
     return;
@@ -534,7 +534,7 @@ void HistoryService::AddPageNoVisitForBookmark(const GURL& url,
 }
 
 void HistoryService::SetPageTitle(const GURL& url,
-                                  const string16& title) {
+                                  const base::string16& title) {
   DCHECK(thread_checker_.CalledOnValidThread());
   ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::SetPageTitle, url, title);
 }
@@ -549,7 +549,7 @@ void HistoryService::UpdateWithPageEndTime(const void* host,
 }
 
 void HistoryService::AddPageWithDetails(const GURL& url,
-                                        const string16& title,
+                                        const base::string16& title,
                                         int visit_count,
                                         int typed_count,
                                         Time last_visit,
@@ -842,7 +842,7 @@ void HistoryService::RemoveDownloads(const std::set<uint32>& ids) {
 }
 
 HistoryService::Handle HistoryService::QueryHistory(
-    const string16& text_query,
+    const base::string16& text_query,
     const history::QueryOptions& options,
     CancelableRequestConsumerBase* consumer,
     const QueryHistoryCallback& callback) {
diff --git a/chrome/browser/history/history_service.h b/chrome/browser/history/history_service.h
index 4b322ae..11e5530 100644
--- a/chrome/browser/history/history_service.h
+++ b/chrome/browser/history/history_service.h
@@ -217,11 +217,11 @@ class HistoryService : public CancelableRequestProvider,
   // Adds an entry for the specified url without creating a visit. This should
   // only be used when bookmarking a page, otherwise the row leaks in the
   // history db (it never gets cleaned).
-  void AddPageNoVisitForBookmark(const GURL& url, const string16& title);
+  void AddPageNoVisitForBookmark(const GURL& url, const base::string16& title);
 
   // Sets the title for the given page. The page should be in history. If it
   // is not, this operation is ignored.
-  void SetPageTitle(const GURL& url, const string16& title);
+  void SetPageTitle(const GURL& url, const base::string16& title);
 
   // Updates the history database with a page's ending time stamp information.
   // The page can be identified by the combination of the pointer to
@@ -267,7 +267,7 @@ class HistoryService : public CancelableRequestProvider,
   // Queries all history with the given options (see QueryOptions in
   // history_types.h).  If empty, all results matching the given options
   // will be returned.
-  Handle QueryHistory(const string16& text_query,
+  Handle QueryHistory(const base::string16& text_query,
                       const history::QueryOptions& options,
                       CancelableRequestConsumerBase* consumer,
                       const QueryHistoryCallback& callback);
@@ -487,7 +487,7 @@ class HistoryService : public CancelableRequestProvider,
   // id of the url, keyword_id the id of the keyword and term the search term.
   void SetKeywordSearchTermsForURL(const GURL& url,
                                    TemplateURLID keyword_id,
-                                   const string16& term);
+                                   const base::string16& term);
 
   // Deletes all search terms for the specified keyword.
   void DeleteAllSearchTermsForKeyword(TemplateURLID keyword_id);
@@ -502,7 +502,7 @@ class HistoryService : public CancelableRequestProvider,
   // first.
   Handle GetMostRecentKeywordSearchTerms(
       TemplateURLID keyword_id,
-      const string16& prefix,
+      const base::string16& prefix,
       int max_count,
       CancelableRequestConsumerBase* consumer,
       const GetMostRecentKeywordSearchTermsCallback& callback);
@@ -556,7 +556,7 @@ class HistoryService : public CancelableRequestProvider,
   // visit using the |last_visit| timestamp, and a PageTransition type of LINK,
   // if |visit_source| != SYNCED.
   void AddPageWithDetails(const GURL& url,
-                          const string16& title,
+                          const base::string16& title,
                           int visit_count,
                           int typed_count,
                           base::Time last_visit,
diff --git a/chrome/browser/history/history_types.cc b/chrome/browser/history/history_types.cc
index 959d118..283c55b 100644
--- a/chrome/browser/history/history_types.cc
+++ b/chrome/browser/history/history_types.cc
@@ -282,13 +282,13 @@ KeywordSearchTermRow::~KeywordSearchTermRow() {}
 MostVisitedURL::MostVisitedURL() {}
 
 MostVisitedURL::MostVisitedURL(const GURL& url,
-                               const string16& title)
+                               const base::string16& title)
     : url(url),
       title(title) {
 }
 
 MostVisitedURL::MostVisitedURL(const GURL& url,
-                               const string16& title,
+                               const base::string16& title,
                                const base::Time& last_forced_time)
     : url(url),
       title(title),
diff --git a/chrome/browser/history/history_types.h b/chrome/browser/history/history_types.h
index a24a79a..2fac614 100644
--- a/chrome/browser/history/history_types.h
+++ b/chrome/browser/history/history_types.h
@@ -86,10 +86,10 @@ class URLRow {
 
   const GURL& url() const { return url_; }
 
-  const string16& title() const {
+  const base::string16& title() const {
     return title_;
   }
-  void set_title(const string16& title) {
+  void set_title(const base::string16& title) {
     // The title is frequently set to the same thing, so we don't bother
     // updating unless the string has changed.
     if (title != title_) {
@@ -173,7 +173,7 @@ class URLRow {
   // the constructor to make a new one.
   GURL url_;
 
-  string16 title_;
+  base::string16 title_;
 
   // Total number of times this URL has been visited.
   int visit_count_;
@@ -486,7 +486,7 @@ struct KeywordSearchTermVisit {
   KeywordSearchTermVisit();
   ~KeywordSearchTermVisit();
 
-  string16 term;    // The search term that was used.
+  base::string16 term;    // The search term that was used.
   int visits;       // The visit count.
   base::Time time;  // The time of the most recent visit.
 };
@@ -500,7 +500,7 @@ struct KeywordSearchTermRow {
 
   TemplateURLID keyword_id;  // ID of the keyword.
   URLID url_id;              // ID of the url.
-  string16 term;             // The search term that was used.
+  base::string16 term;             // The search term that was used.
 };
 
 // MostVisitedURL --------------------------------------------------------------
@@ -508,14 +508,14 @@ struct KeywordSearchTermRow {
 // Holds the per-URL information of the most visited query.
 struct MostVisitedURL {
   MostVisitedURL();
-  MostVisitedURL(const GURL& url, const string16& title);
+  MostVisitedURL(const GURL& url, const base::string16& title);
   MostVisitedURL(const GURL& url,
-                 const string16& title,
+                 const base::string16& title,
                  const base::Time& last_forced_time);
   ~MostVisitedURL();
 
   GURL url;
-  string16 title;
+  base::string16 title;
 
   // If this is a URL for which we want to force a thumbnail, records the last
   // time it was forced so we can evict it when more recent URLs are requested.
@@ -550,7 +550,7 @@ struct FilteredURL {
   ~FilteredURL();
 
   GURL url;
-  string16 title;
+  base::string16 title;
   double score;
   ExtendedInfo extended_info;
 };
diff --git a/chrome/browser/history/history_unittest.cc b/chrome/browser/history/history_unittest.cc
index d8b5e80..21ce21a 100644
--- a/chrome/browser/history/history_unittest.cc
+++ b/chrome/browser/history/history_unittest.cc
@@ -1274,7 +1274,7 @@ TEST_F(HistoryTest, SetTitle) {
       existing_url, base::Time::Now(), history::SOURCE_BROWSED);
 
   // Set some title.
-  const string16 existing_title = UTF8ToUTF16("Google");
+  const base::string16 existing_title = UTF8ToUTF16("Google");
   history_service_->SetPageTitle(existing_url, existing_title);
 
   // Make sure the title got set.
@@ -1283,7 +1283,7 @@ TEST_F(HistoryTest, SetTitle) {
 
   // set a title on a nonexistent page
   const GURL nonexistent_url("http://news.google.com/");
-  const string16 nonexistent_title = UTF8ToUTF16("Google News");
+  const base::string16 nonexistent_title = UTF8ToUTF16("Google News");
   history_service_->SetPageTitle(nonexistent_url, nonexistent_title);
 
   // Make sure nothing got written.
@@ -1826,7 +1826,7 @@ TEST_F(HistoryBackendDBTest, MigratePresentations) {
   const URLID url_id = 3;
   const GURL url("http://www.foo.com");
   const std::string url_name(VisitSegmentDatabase::ComputeSegmentName(url));
-  const string16 title(ASCIIToUTF16("Title1"));
+  const base::string16 title(ASCIIToUTF16("Title1"));
   const Time segment_time(Time::Now());
 
   {
diff --git a/chrome/browser/history/in_memory_url_index.cc b/chrome/browser/history/in_memory_url_index.cc
index 2ce9695..4c2d53c 100644
--- a/chrome/browser/history/in_memory_url_index.cc
+++ b/chrome/browser/history/in_memory_url_index.cc
@@ -160,7 +160,7 @@ bool InMemoryURLIndex::GetCacheFilePath(base::FilePath* file_path) {
 // Querying --------------------------------------------------------------------
 
 ScoredHistoryMatches InMemoryURLIndex::HistoryItemsForTerms(
-    const string16& term_string,
+    const base::string16& term_string,
     size_t cursor_position) {
   return private_data_->HistoryItemsForTerms(
       term_string,
diff --git a/chrome/browser/history/in_memory_url_index.h b/chrome/browser/history/in_memory_url_index.h
index 8033ee9..1279c32 100644
--- a/chrome/browser/history/in_memory_url_index.h
+++ b/chrome/browser/history/in_memory_url_index.h
@@ -117,10 +117,10 @@ class InMemoryURLIndex : public content::NotificationObserver,
   // Scans the history index and returns a vector with all scored, matching
   // history items. This entry point simply forwards the call on to the
   // URLIndexPrivateData class. For a complete description of this function
-  // refer to that class.  If |cursor_position| is string16::npos, the
+  // refer to that class.  If |cursor_position| is base::string16::npos, the
   // function doesn't do anything special with the cursor; this is equivalent
   // to the cursor being at the end.
-  ScoredHistoryMatches HistoryItemsForTerms(const string16& term_string,
+  ScoredHistoryMatches HistoryItemsForTerms(const base::string16& term_string,
                                             size_t cursor_position);
 
   // Deletes the index entry, if any, for the given |url|.
diff --git a/chrome/browser/history/in_memory_url_index_types.cc b/chrome/browser/history/in_memory_url_index_types.cc
index e30e2c3..77197be 100644
--- a/chrome/browser/history/in_memory_url_index_types.cc
+++ b/chrome/browser/history/in_memory_url_index_types.cc
@@ -49,18 +49,20 @@ string16 CleanUpUrlForMatching(const GURL& gurl,
       NULL, NULL, NULL));
 }
 
-string16 CleanUpTitleForMatching(const string16& title) {
+string16 CleanUpTitleForMatching(const base::string16& title) {
   return base::i18n::ToLower(title.substr(0u, kCleanedUpTitleMaxLength));
 }
 
-TermMatches MatchTermInString(const string16& term,
-                              const string16& cleaned_string,
+TermMatches MatchTermInString(const base::string16& term,
+                              const base::string16& cleaned_string,
                               int term_num) {
   const size_t kMaxCompareLength = 2048;
-  const string16& short_string = (cleaned_string.length() > kMaxCompareLength) ?
+  const base::string16& short_string =
+      (cleaned_string.length() > kMaxCompareLength) ?
       cleaned_string.substr(0, kMaxCompareLength) : cleaned_string;
   TermMatches matches;
-  for (size_t location = short_string.find(term); location != string16::npos;
+  for (size_t location = short_string.find(term);
+       location != base::string16::npos;
        location = short_string.find(term, location + 1))
     matches.push_back(TermMatch(term_num, location, term.length()));
   return matches;
@@ -102,7 +104,7 @@ TermMatches ReplaceOffsetsInTermMatches(const TermMatches& matches,
   std::vector<size_t>::const_iterator offset_iter = offsets.begin();
   for (TermMatches::const_iterator term_iter = matches.begin();
        term_iter != matches.end(); ++term_iter, ++offset_iter) {
-    if (*offset_iter != string16::npos) {
+    if (*offset_iter != base::string16::npos) {
       TermMatch new_match(*term_iter);
       new_match.offset = *offset_iter;
       new_matches.push_back(new_match);
@@ -113,7 +115,7 @@ TermMatches ReplaceOffsetsInTermMatches(const TermMatches& matches,
 
 // Utility Functions -----------------------------------------------------------
 
-String16Set String16SetFromString16(const string16& cleaned_uni_string,
+String16Set String16SetFromString16(const base::string16& cleaned_uni_string,
                                     WordStarts* word_starts) {
   String16Vector words =
       String16VectorFromString16(cleaned_uni_string, false, word_starts);
@@ -124,9 +126,10 @@ String16Set String16SetFromString16(const string16& cleaned_uni_string,
   return word_set;
 }
 
-String16Vector String16VectorFromString16(const string16& cleaned_uni_string,
-                                          bool break_on_space,
-                                          WordStarts* word_starts) {
+String16Vector String16VectorFromString16(
+    const base::string16& cleaned_uni_string,
+    bool break_on_space,
+    WordStarts* word_starts) {
   if (word_starts)
     word_starts->clear();
   base::i18n::BreakIterator iter(cleaned_uni_string,
@@ -137,10 +140,10 @@ String16Vector String16VectorFromString16(const string16& cleaned_uni_string,
     return words;
   while (iter.Advance()) {
     if (break_on_space || iter.IsWord()) {
-      string16 word(iter.GetString());
+      base::string16 word(iter.GetString());
       size_t initial_whitespace = 0;
       if (break_on_space) {
-        string16 trimmed_word;
+        base::string16 trimmed_word;
         TrimWhitespace(word, TRIM_LEADING, &trimmed_word);
         initial_whitespace = word.length() - trimmed_word.length();
         TrimWhitespace(trimmed_word, TRIM_TRAILING, &word);
@@ -158,7 +161,7 @@ String16Vector String16VectorFromString16(const string16& cleaned_uni_string,
   return words;
 }
 
-Char16Set Char16SetFromString16(const string16& term) {
+Char16Set Char16SetFromString16(const base::string16& term) {
   Char16Set characters;
   for (string16::const_iterator iter = term.begin(); iter != term.end(); ++iter)
     characters.insert(*iter);
diff --git a/chrome/browser/history/in_memory_url_index_types.h b/chrome/browser/history/in_memory_url_index_types.h
index 243f5ef..976e062 100644
--- a/chrome/browser/history/in_memory_url_index_types.h
+++ b/chrome/browser/history/in_memory_url_index_types.h
@@ -46,12 +46,12 @@ typedef std::vector<TermMatch> TermMatches;
 // no longer match this URL.  Note that the resulting unescaped URL
 // may not be directly navigable (which is why we escaped it to begin
 // with).  |languages| is passed to net::FormatUrl().
-string16 CleanUpUrlForMatching(const GURL& gurl,
-                               const std::string& languages);
+base::string16 CleanUpUrlForMatching(const GURL& gurl,
+                                     const std::string& languages);
 
 // Returns the lower-cased title, possibly truncated if the original title
 // is overly-long.
-string16 CleanUpTitleForMatching(const string16& title);
+base::string16 CleanUpTitleForMatching(const base::string16& title);
 
 // Returns a TermMatches which has an entry for each occurrence of the
 // string |term| found in the string |cleaned_string|. Use
@@ -61,8 +61,8 @@ string16 CleanUpTitleForMatching(const string16& title);
 // with other TermMatches for other terms. Note that only the first
 // 2,048 characters of |string| are considered during the match
 // operation.
-TermMatches MatchTermInString(const string16& term,
-                              const string16& cleaned_string,
+TermMatches MatchTermInString(const base::string16& term,
+                              const base::string16& cleaned_string,
                               int term_num);
 
 // Sorts and removes overlapping substring matches from |matches| and
@@ -79,8 +79,8 @@ TermMatches ReplaceOffsetsInTermMatches(const TermMatches& matches,
 
 // Convenience Types -----------------------------------------------------------
 
-typedef std::vector<string16> String16Vector;
-typedef std::set<string16> String16Set;
+typedef std::vector<base::string16> String16Vector;
+typedef std::set<base::string16> String16Set;
 typedef std::set<char16> Char16Set;
 typedef std::vector<char16> Char16Vector;
 
@@ -96,7 +96,7 @@ typedef std::vector<size_t> WordStarts;
 // |cleaned_uni_string| at which each word starts onto
 // |word_starts|. These offsets are collected only up to the first
 // kMaxSignificantChars of |cleaned_uni_string|.
-String16Set String16SetFromString16(const string16& cleaned_uni_string,
+String16Set String16SetFromString16(const base::string16& cleaned_uni_string,
                                     WordStarts* word_starts);
 
 // Breaks the |cleaned_uni_string| string down into individual words
@@ -118,9 +118,10 @@ String16Set String16SetFromString16(const string16& cleaned_uni_string,
 //    "http", "www", "google", "com", "harry", "the", "rabbit"
 //   With |break_on_space| true the returned list will contain:
 //    "http://", "www.google.com/", "harry", "the", "rabbit."
-String16Vector String16VectorFromString16(const string16& cleaned_uni_string,
-                                          bool break_on_space,
-                                          WordStarts* word_starts);
+String16Vector String16VectorFromString16(
+    const base::string16& cleaned_uni_string,
+    bool break_on_space,
+    WordStarts* word_starts);
 
 // Breaks the |uni_word| string down into its individual characters.
 // Note that this is temporarily intended to work on a single word, but
@@ -130,7 +131,7 @@ String16Vector String16VectorFromString16(const string16& cleaned_uni_string,
 // and properly handle substring matches, scoring and sorting the results
 // by score. Also, provide the metrics for where the matches occur so that
 // the UI can highlight the matched sections.
-Char16Set Char16SetFromString16(const string16& uni_word);
+Char16Set Char16SetFromString16(const base::string16& uni_word);
 
 // Support for InMemoryURLIndex Private Data -----------------------------------
 
@@ -138,7 +139,7 @@ Char16Set Char16SetFromString16(const string16& uni_word);
 typedef size_t WordID;
 
 // A map allowing a WordID to be determined given a word.
-typedef std::map<string16, WordID> WordMap;
+typedef std::map<base::string16, WordID> WordMap;
 
 // A map from character to the word_ids of words containing that character.
 typedef std::set<WordID> WordIDSet;  // An index into the WordList.
diff --git a/chrome/browser/history/in_memory_url_index_types_unittest.cc b/chrome/browser/history/in_memory_url_index_types_unittest.cc
index 4f3a209..f31348b 100644
--- a/chrome/browser/history/in_memory_url_index_types_unittest.cc
+++ b/chrome/browser/history/in_memory_url_index_types_unittest.cc
@@ -30,7 +30,7 @@ class InMemoryURLIndexTypesTest : public testing::Test {
 
 TEST_F(InMemoryURLIndexTypesTest, StaticFunctions) {
   // Test String16VectorFromString16
-  string16 string_a(ASCIIToUTF16("http://www.google.com/ frammy  the brammy"));
+  base::string16 string_a(ASCIIToUTF16("http://www.google.com/ frammy  the brammy"));
   WordStarts actual_starts_a;
   String16Vector string_vec =
       String16VectorFromString16(string_a, false, &actual_starts_a);
@@ -60,7 +60,7 @@ TEST_F(InMemoryURLIndexTypesTest, StaticFunctions) {
   EXPECT_TRUE(IntArraysEqual(expected_starts_b, arraysize(expected_starts_b),
                              actual_starts_b));
 
-  string16 string_c(ASCIIToUTF16(
+  base::string16 string_c(ASCIIToUTF16(
       " funky%20string-with=@strange   sequences, intended(to exceed)"));
   WordStarts actual_starts_c;
   string_vec = String16VectorFromString16(string_c, false, &actual_starts_c);
@@ -71,7 +71,7 @@ TEST_F(InMemoryURLIndexTypesTest, StaticFunctions) {
                              actual_starts_c));
 
   // Test String16SetFromString16
-  string16 string_d(ASCIIToUTF16(
+  base::string16 string_d(ASCIIToUTF16(
       "http://web.google.com/search Google Web Search"));
   WordStarts actual_starts_d;
   String16Set string_set = String16SetFromString16(string_d, &actual_starts_d);
@@ -135,7 +135,7 @@ TEST_F(InMemoryURLIndexTypesTest, OffsetsAndTermMatches) {
     EXPECT_EQ(expected_offsets_a[i], offsets[i]);
 
   // Test ReplaceOffsetsInTermMatches
-  offsets[2] = string16::npos;
+  offsets[2] = base::string16::npos;
   history::TermMatches matches_b =
       ReplaceOffsetsInTermMatches(matches_a, offsets);
   const size_t expected_offsets_b[] = {1, 4, 10, 14};
diff --git a/chrome/browser/history/in_memory_url_index_unittest.cc b/chrome/browser/history/in_memory_url_index_unittest.cc
index bd2c039..9be82cf3 100644
--- a/chrome/browser/history/in_memory_url_index_unittest.cc
+++ b/chrome/browser/history/in_memory_url_index_unittest.cc
@@ -90,7 +90,7 @@ class InMemoryURLIndexTest : public testing::Test {
   // Validates that the given |term| is contained in |cache| and that it is
   // marked as in-use.
   void CheckTerm(const URLIndexPrivateData::SearchTermCacheMap& cache,
-                 string16 term) const;
+                 base::string16 term) const;
 
   // Pass-through function to simplify our friendship with HistoryService.
   sql::Connection& GetDB();
@@ -283,7 +283,7 @@ base::FilePath::StringType InMemoryURLIndexTest::TestDBName() const {
 
 void InMemoryURLIndexTest::CheckTerm(
     const URLIndexPrivateData::SearchTermCacheMap& cache,
-    string16 term) const {
+    base::string16 term) const {
   URLIndexPrivateData::SearchTermCacheMap::const_iterator cache_iter(
       cache.find(term));
   ASSERT_TRUE(cache.end() != cache_iter)
@@ -444,7 +444,7 @@ TEST_F(LimitedInMemoryURLIndexTest, Initialization) {
 TEST_F(InMemoryURLIndexTest, Retrieval) {
   // See if a very specific term gives a single result.
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudgeReport"), string16::npos);
+      ASCIIToUTF16("DrudgeReport"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // Verify that we got back the result we expected.
@@ -456,7 +456,7 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
   // Make sure a trailing space prevents inline-ability but still results
   // in the expected result.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("DrudgeReport "),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(5, matches[0].url_info.id());
   EXPECT_EQ("http://drudgereport.com/", matches[0].url_info.url().spec());
@@ -465,14 +465,14 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
 
   // Search which should result in multiple results.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("drudge"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(2U, matches.size());
   // The results should be in descending score order.
   EXPECT_GE(matches[0].raw_score(), matches[1].raw_score());
 
   // Search which should result in nearly perfect result.
   matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("Nearly Perfect Result"), string16::npos);
+      ASCIIToUTF16("Nearly Perfect Result"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   // The results should have a very high score.
   EXPECT_GT(matches[0].raw_score(), 900);
@@ -485,7 +485,7 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
 
   // Search which should result in very poor result.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("qui c"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   // The results should have a poor score.
   EXPECT_LT(matches[0].raw_score(), 500);
@@ -498,14 +498,14 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
 
   // Search which will match at the end of an URL with encoded characters.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("Mice"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(30, matches[0].url_info.id());
   EXPECT_FALSE(matches[0].can_inline());
 
   // Check that URLs are not escaped an escape time.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("1% wikipedia"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(35, matches[0].url_info.id());
   EXPECT_EQ("http://en.wikipedia.org/wiki/1%25_rule_(Internet_culture)",
@@ -514,7 +514,7 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
   // Verify that a single term can appear multiple times in the URL and as long
   // as one starts the URL it is still inlined.
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("fubar"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(34, matches[0].url_info.id());
   EXPECT_EQ("http://fubarfubarandfubar.com/", matches[0].url_info.url().spec());
@@ -526,7 +526,7 @@ TEST_F(InMemoryURLIndexTest, Retrieval) {
 TEST_F(InMemoryURLIndexTest, CursorPositionRetrieval) {
   // See if a very specific term with no cursor gives an empty result.
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudReport"), string16::npos);
+      ASCIIToUTF16("DrudReport"), base::string16::npos);
   ASSERT_EQ(0U, matches.size());
 
   // The same test with the cursor at the end should give an empty result.
@@ -543,7 +543,7 @@ TEST_F(InMemoryURLIndexTest, CursorPositionRetrieval) {
   // Now check multi-word inputs.  No cursor should fail to find a
   // result on this input.
   matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("MORTGAGERATE DROPS"), string16::npos);
+      ASCIIToUTF16("MORTGAGERATE DROPS"), base::string16::npos);
   ASSERT_EQ(0U, matches.size());
 
   // Ditto with cursor at end.
@@ -566,61 +566,61 @@ TEST_F(InMemoryURLIndexTest, CursorPositionRetrieval) {
 TEST_F(InMemoryURLIndexTest, URLPrefixMatching) {
   // "drudgere" - found, can inline
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("drudgere"), string16::npos);
+      ASCIIToUTF16("drudgere"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
   // "drudgere" - found, can inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("drudgere"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
   // "www.atdmt" - not found
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("www.atdmt"),
-                                             string16::npos);
+                                             base::string16::npos);
   EXPECT_EQ(0U, matches.size());
 
   // "atdmt" - found, cannot inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("atdmt"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_FALSE(matches[0].can_inline());
 
   // "view.atdmt" - found, can inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("view.atdmt"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
   // "view.atdmt" - found, can inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("view.atdmt"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
   // "cnn.com" - found, can inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("cnn.com"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(2U, matches.size());
   // One match should be inline-able, the other not.
   EXPECT_TRUE(matches[0].can_inline() != matches[1].can_inline());
 
   // "www.cnn.com" - found, can inline
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("www.cnn.com"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
   // "ww.cnn.com" - found because we allow mid-term matches in hostnames
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("ww.cnn.com"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // "www.cnn.com" - found, can inline
   matches =
       url_index_->HistoryItemsForTerms(ASCIIToUTF16("www.cnn.com"),
-                                       string16::npos);
+                                       base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_TRUE(matches[0].can_inline());
 
@@ -628,7 +628,7 @@ TEST_F(InMemoryURLIndexTest, URLPrefixMatching) {
   // match
   matches =
       url_index_->HistoryItemsForTerms(ASCIIToUTF16("tp://www.cnn.com"),
-                                       string16::npos);
+                                       base::string16::npos);
   ASSERT_EQ(0U, matches.size());
 }
 
@@ -638,13 +638,13 @@ TEST_F(InMemoryURLIndexTest, ProperStringMatching) {
   // "atdmt.view" - not found
   // "view.atdmt" - found
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("atdmt view"), string16::npos);
+      ASCIIToUTF16("atdmt view"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("atdmt.view"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(0U, matches.size());
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("view.atdmt"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 }
 
@@ -657,7 +657,7 @@ TEST_F(InMemoryURLIndexTest, HugeResultSet) {
   }
 
   ScoredHistoryMatches matches =
-      url_index_->HistoryItemsForTerms(ASCIIToUTF16("b"), string16::npos);
+      url_index_->HistoryItemsForTerms(ASCIIToUTF16("b"), base::string16::npos);
   URLIndexPrivateData& private_data(*GetPrivateData());
   ASSERT_EQ(AutocompleteProvider::kMaxMatches, matches.size());
   // There are 7 matches already in the database.
@@ -673,7 +673,7 @@ TEST_F(InMemoryURLIndexTest, TitleSearch) {
 
   // Ensure title is being searched.
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("MORTGAGE RATE DROPS"), string16::npos);
+      ASCIIToUTF16("MORTGAGE RATE DROPS"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // Verify that we got back the result we expected.
@@ -687,10 +687,10 @@ TEST_F(InMemoryURLIndexTest, TitleSearch) {
 
 TEST_F(InMemoryURLIndexTest, TitleChange) {
   // Verify current title terms retrieves desired item.
-  string16 original_terms =
+  base::string16 original_terms =
       ASCIIToUTF16("lebronomics could high taxes influence");
   ScoredHistoryMatches matches =
-      url_index_->HistoryItemsForTerms(original_terms, string16::npos);
+      url_index_->HistoryItemsForTerms(original_terms, base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // Verify that we got back the result we expected.
@@ -704,8 +704,8 @@ TEST_F(InMemoryURLIndexTest, TitleChange) {
   URLRow old_row(matches[0].url_info);
 
   // Verify new title terms retrieves nothing.
-  string16 new_terms = ASCIIToUTF16("does eat oats little lambs ivy");
-  matches = url_index_->HistoryItemsForTerms(new_terms, string16::npos);
+  base::string16 new_terms = ASCIIToUTF16("does eat oats little lambs ivy");
+  matches = url_index_->HistoryItemsForTerms(new_terms, base::string16::npos);
   ASSERT_EQ(0U, matches.size());
 
   // Update the row.
@@ -713,10 +713,11 @@ TEST_F(InMemoryURLIndexTest, TitleChange) {
   EXPECT_TRUE(UpdateURL(old_row));
 
   // Verify we get the row using the new terms but not the original terms.
-  matches = url_index_->HistoryItemsForTerms(new_terms, string16::npos);
+  matches = url_index_->HistoryItemsForTerms(new_terms, base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(expected_id, matches[0].url_info.id());
-  matches = url_index_->HistoryItemsForTerms(original_terms, string16::npos);
+  matches =
+      url_index_->HistoryItemsForTerms(original_terms, base::string16::npos);
   ASSERT_EQ(0U, matches.size());
 }
 
@@ -724,29 +725,30 @@ TEST_F(InMemoryURLIndexTest, NonUniqueTermCharacterSets) {
   // The presence of duplicate characters should succeed. Exercise by cycling
   // through a string with several duplicate characters.
   ScoredHistoryMatches matches =
-      url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRA"), string16::npos);
+      url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRA"),
+                                       base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(28, matches[0].url_info.id());
   EXPECT_EQ("http://www.ddj.com/windows/184416623",
             matches[0].url_info.url().spec());
 
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRACAD"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(28, matches[0].url_info.id());
 
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRACADABRA"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(28, matches[0].url_info.id());
 
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRACADABR"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(28, matches[0].url_info.id());
 
   matches = url_index_->HistoryItemsForTerms(ASCIIToUTF16("ABRACA"),
-                                             string16::npos);
+                                             base::string16::npos);
   ASSERT_EQ(1U, matches.size());
   EXPECT_EQ(28, matches[0].url_info.id());
 }
@@ -769,20 +771,21 @@ TEST_F(InMemoryURLIndexTest, TypedCharacterCaching) {
 
   // Simulate typing "r" giving "r" in the simulated omnibox. The results for
   // 'r' will be not cached because it is only 1 character long.
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r"), base::string16::npos);
   EXPECT_EQ(0U, cache.size());
 
   // Simulate typing "re" giving "r re" in the simulated omnibox.
   // 're' should be cached at this point but not 'r' as it is a single
   // character.
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r re"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r re"), base::string16::npos);
   ASSERT_EQ(1U, cache.size());
   CheckTerm(cache, ASCIIToUTF16("re"));
 
   // Simulate typing "reco" giving "r re reco" in the simulated omnibox.
   // 're' and 'reco' should be cached at this point but not 'r' as it is a
   // single character.
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r re reco"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("r re reco"),
+                                   base::string16::npos);
   ASSERT_EQ(2U, cache.size());
   CheckTerm(cache, ASCIIToUTF16("re"));
   CheckTerm(cache, ASCIIToUTF16("reco"));
@@ -790,18 +793,20 @@ TEST_F(InMemoryURLIndexTest, TypedCharacterCaching) {
   // Simulate typing "mort".
   // Since we now have only one search term, the cached results for 're' and
   // 'reco' should be purged, giving us only 1 item in the cache (for 'mort').
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort"), base::string16::npos);
   ASSERT_EQ(1U, cache.size());
   CheckTerm(cache, ASCIIToUTF16("mort"));
 
   // Simulate typing "reco" giving "mort reco" in the simulated omnibox.
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort reco"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort reco"),
+                                   base::string16::npos);
   ASSERT_EQ(2U, cache.size());
   CheckTerm(cache, ASCIIToUTF16("mort"));
   CheckTerm(cache, ASCIIToUTF16("reco"));
 
   // Simulate a <DELETE> by removing the 'reco' and adding back the 'rec'.
-  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort rec"), string16::npos);
+  url_index_->HistoryItemsForTerms(ASCIIToUTF16("mort rec"),
+                                   base::string16::npos);
   ASSERT_EQ(2U, cache.size());
   CheckTerm(cache, ASCIIToUTF16("mort"));
   CheckTerm(cache, ASCIIToUTF16("rec"));
@@ -813,7 +818,7 @@ TEST_F(InMemoryURLIndexTest, AddNewRows) {
   // Newly created URLRows get a last_visit time of 'right now' so it should
   // qualify as a quick result candidate.
   EXPECT_TRUE(url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("brokeandalone"), string16::npos).empty());
+      ASCIIToUTF16("brokeandalone"), base::string16::npos).empty());
 
   // Add a new row.
   URLRow new_row(GURL("http://www.brokeandaloneinmanitoba.com/"), new_row_id++);
@@ -822,13 +827,13 @@ TEST_F(InMemoryURLIndexTest, AddNewRows) {
 
   // Verify that we can retrieve it.
   EXPECT_EQ(1U, url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("brokeandalone"), string16::npos).size());
+      ASCIIToUTF16("brokeandalone"), base::string16::npos).size());
 
   // Add it again just to be sure that is harmless and that it does not update
   // the index.
   EXPECT_FALSE(UpdateURL(new_row));
   EXPECT_EQ(1U, url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("brokeandalone"), string16::npos).size());
+      ASCIIToUTF16("brokeandalone"), base::string16::npos).size());
 
   // Make up an URL that does not qualify and try to add it.
   URLRow unqualified_row(GURL("http://www.brokeandaloneinmanitoba.com/"),
@@ -838,13 +843,13 @@ TEST_F(InMemoryURLIndexTest, AddNewRows) {
 
 TEST_F(InMemoryURLIndexTest, DeleteRows) {
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudgeReport"), string16::npos);
+      ASCIIToUTF16("DrudgeReport"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // Delete the URL then search again.
   EXPECT_TRUE(DeleteURL(matches[0].url_info.url()));
   EXPECT_TRUE(url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudgeReport"), string16::npos).empty());
+      ASCIIToUTF16("DrudgeReport"), base::string16::npos).empty());
 
   // Make up an URL that does not exist in the database and delete it.
   GURL url("http://www.hokeypokey.com/putyourrightfootin.html");
@@ -853,7 +858,7 @@ TEST_F(InMemoryURLIndexTest, DeleteRows) {
 
 TEST_F(InMemoryURLIndexTest, ExpireRow) {
   ScoredHistoryMatches matches = url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudgeReport"), string16::npos);
+      ASCIIToUTF16("DrudgeReport"), base::string16::npos);
   ASSERT_EQ(1U, matches.size());
 
   // Determine the row id for the result, remember that id, broadcast a
@@ -865,7 +870,7 @@ TEST_F(InMemoryURLIndexTest, ExpireRow) {
           content::Source<InMemoryURLIndexTest>(this),
           content::Details<history::HistoryDetails>(&deleted_details));
   EXPECT_TRUE(url_index_->HistoryItemsForTerms(
-      ASCIIToUTF16("DrudgeReport"), string16::npos).empty());
+      ASCIIToUTF16("DrudgeReport"), base::string16::npos).empty());
 }
 
 TEST_F(InMemoryURLIndexTest, WhitelistedURLs) {
diff --git a/chrome/browser/history/page_usage_data.h b/chrome/browser/history/page_usage_data.h
index 07f58dd..582f1c3 100644
--- a/chrome/browser/history/page_usage_data.h
+++ b/chrome/browser/history/page_usage_data.h
@@ -41,11 +41,11 @@ class PageUsageData {
     return url_;
   }
 
-  void SetTitle(const string16& s) {
+  void SetTitle(const base::string16& s) {
     title_ = s;
   }
 
-  const string16& GetTitle() const {
+  const base::string16& GetTitle() const {
     return title_;
   }
 
@@ -71,7 +71,7 @@ class PageUsageData {
  private:
   history::SegmentID id_;
   GURL url_;
-  string16 title_;
+  base::string16 title_;
 
   double score_;
 
diff --git a/chrome/browser/history/query_parser.cc b/chrome/browser/history/query_parser.cc
index 322da23..f61de1a 100644
--- a/chrome/browser/history/query_parser.cc
+++ b/chrome/browser/history/query_parser.cc
@@ -75,17 +75,17 @@ bool IsQueryQuote(wchar_t ch) {
 // A QueryNodeWord is a single word in the query.
 class QueryNodeWord : public QueryNode {
  public:
-  explicit QueryNodeWord(const string16& word);
+  explicit QueryNodeWord(const base::string16& word);
   virtual ~QueryNodeWord();
 
-  const string16& word() const { return word_; }
+  const base::string16& word() const { return word_; }
 
   void set_literal(bool literal) { literal_ = literal; }
 
   // QueryNode:
   virtual int AppendToSQLiteQuery(string16* query) const OVERRIDE;
   virtual bool IsWord() const OVERRIDE;
-  virtual bool Matches(const string16& word, bool exact) const OVERRIDE;
+  virtual bool Matches(const base::string16& word, bool exact) const OVERRIDE;
   virtual bool HasMatchIn(
       const std::vector<QueryWord>& words,
       Snippet::MatchPositions* match_positions) const OVERRIDE;
@@ -94,13 +94,13 @@ class QueryNodeWord : public QueryNode {
   virtual void AppendWords(std::vector<string16>* words) const OVERRIDE;
 
  private:
-  string16 word_;
+  base::string16 word_;
   bool literal_;
 
   DISALLOW_COPY_AND_ASSIGN(QueryNodeWord);
 };
 
-QueryNodeWord::QueryNodeWord(const string16& word)
+QueryNodeWord::QueryNodeWord(const base::string16& word)
     : word_(word),
       literal_(false) {}
 
@@ -119,7 +119,7 @@ bool QueryNodeWord::IsWord() const {
   return true;
 }
 
-bool QueryNodeWord::Matches(const string16& word, bool exact) const {
+bool QueryNodeWord::Matches(const base::string16& word, bool exact) const {
   if (exact || !QueryParser::IsWordLongEnoughForPrefixSearch(word_))
     return word == word_;
   return word.size() >= word_.size() &&
@@ -149,7 +149,7 @@ bool QueryNodeWord::HasMatchIn(const std::vector<QueryWord>& words) const {
   return false;
 }
 
-void QueryNodeWord::AppendWords(std::vector<string16>* words) const {
+void QueryNodeWord::AppendWords(std::vector<base::string16>* words) const {
   words->push_back(word_);
 }
 
@@ -169,18 +169,18 @@ class QueryNodeList : public QueryNode {
   void RemoveEmptySubnodes();
 
   // QueryNode:
-  virtual int AppendToSQLiteQuery(string16* query) const OVERRIDE;
+  virtual int AppendToSQLiteQuery(base::string16* query) const OVERRIDE;
   virtual bool IsWord() const OVERRIDE;
-  virtual bool Matches(const string16& word, bool exact) const OVERRIDE;
+  virtual bool Matches(const base::string16& word, bool exact) const OVERRIDE;
   virtual bool HasMatchIn(
       const std::vector<QueryWord>& words,
       Snippet::MatchPositions* match_positions) const OVERRIDE;
   virtual bool HasMatchIn(
       const std::vector<QueryWord>& words) const OVERRIDE;
-  virtual void AppendWords(std::vector<string16>* words) const OVERRIDE;
+  virtual void AppendWords(std::vector<base::string16>* words) const OVERRIDE;
 
  protected:
-  int AppendChildrenToString(string16* query) const;
+  int AppendChildrenToString(base::string16* query) const;
 
   QueryNodeVector children_;
 
@@ -213,7 +213,7 @@ void QueryNodeList::RemoveEmptySubnodes() {
   }
 }
 
-int QueryNodeList::AppendToSQLiteQuery(string16* query) const {
+int QueryNodeList::AppendToSQLiteQuery(base::string16* query) const {
   return AppendChildrenToString(query);
 }
 
@@ -221,7 +221,7 @@ bool QueryNodeList::IsWord() const {
   return false;
 }
 
-bool QueryNodeList::Matches(const string16& word, bool exact) const {
+bool QueryNodeList::Matches(const base::string16& word, bool exact) const {
   NOTREACHED();
   return false;
 }
@@ -237,12 +237,12 @@ bool QueryNodeList::HasMatchIn(const std::vector<QueryWord>& words) const {
   return false;
 }
 
-void QueryNodeList::AppendWords(std::vector<string16>* words) const {
+void QueryNodeList::AppendWords(std::vector<base::string16>* words) const {
   for (size_t i = 0; i < children_.size(); ++i)
     children_[i]->AppendWords(words);
 }
 
-int QueryNodeList::AppendChildrenToString(string16* query) const {
+int QueryNodeList::AppendChildrenToString(base::string16* query) const {
   int num_words = 0;
   for (QueryNodeVector::const_iterator node = children_.begin();
        node != children_.end(); ++node) {
@@ -260,7 +260,7 @@ class QueryNodePhrase : public QueryNodeList {
   virtual ~QueryNodePhrase();
 
   // QueryNodeList:
-  virtual int AppendToSQLiteQuery(string16* query) const OVERRIDE;
+  virtual int AppendToSQLiteQuery(base::string16* query) const OVERRIDE;
   virtual bool HasMatchIn(
       const std::vector<QueryWord>& words,
       Snippet::MatchPositions* match_positions) const OVERRIDE;
@@ -278,7 +278,7 @@ QueryNodePhrase::QueryNodePhrase() {}
 
 QueryNodePhrase::~QueryNodePhrase() {}
 
-int QueryNodePhrase::AppendToSQLiteQuery(string16* query) const {
+int QueryNodePhrase::AppendToSQLiteQuery(base::string16* query) const {
   query->push_back(L'"');
   int num_words = AppendChildrenToString(query);
   query->push_back(L'"');
@@ -332,7 +332,7 @@ bool QueryNodePhrase::HasMatchIn(const std::vector<QueryWord>& words) const {
 QueryParser::QueryParser() {}
 
 // static
-bool QueryParser::IsWordLongEnoughForPrefixSearch(const string16& word) {
+bool QueryParser::IsWordLongEnoughForPrefixSearch(const base::string16& word) {
   DCHECK(!word.empty());
   size_t minimum_length = 3;
   // We intentionally exclude Hangul Jamos (both Conjoining and compatibility)
@@ -343,14 +343,15 @@ bool QueryParser::IsWordLongEnoughForPrefixSearch(const string16& word) {
   return word.size() >= minimum_length;
 }
 
-int QueryParser::ParseQuery(const string16& query, string16* sqlite_query) {
+int QueryParser::ParseQuery(const base::string16& query,
+                            base::string16* sqlite_query) {
   QueryNodeList root;
   if (!ParseQueryImpl(query, &root))
     return 0;
   return root.AppendToSQLiteQuery(sqlite_query);
 }
 
-void QueryParser::ParseQueryWords(const string16& query,
+void QueryParser::ParseQueryWords(const base::string16& query,
                                   std::vector<string16>* words) {
   QueryNodeList root;
   if (!ParseQueryImpl(query, &root))
@@ -358,21 +359,21 @@ void QueryParser::ParseQueryWords(const string16& query,
   root.AppendWords(words);
 }
 
-void QueryParser::ParseQueryNodes(const string16& query,
+void QueryParser::ParseQueryNodes(const base::string16& query,
                                   std::vector<QueryNode*>* nodes) {
   QueryNodeList root;
   if (ParseQueryImpl(base::i18n::ToLower(query), &root))
     nodes->swap(*root.children());
 }
 
-bool QueryParser::DoesQueryMatch(const string16& text,
+bool QueryParser::DoesQueryMatch(const base::string16& text,
                                  const std::vector<QueryNode*>& query_nodes,
                                  Snippet::MatchPositions* match_positions) {
   if (query_nodes.empty())
     return false;
 
   std::vector<QueryWord> query_words;
-  string16 lower_text = base::i18n::ToLower(text);
+  base::string16 lower_text = base::i18n::ToLower(text);
   ExtractQueryWords(lower_text, &query_words);
 
   if (query_words.empty())
@@ -408,7 +409,8 @@ bool QueryParser::DoesQueryMatch(const std::vector<QueryWord>& query_words,
   return true;
 }
 
-bool QueryParser::ParseQueryImpl(const string16& query, QueryNodeList* root) {
+bool QueryParser::ParseQueryImpl(const base::string16& query,
+                                 QueryNodeList* root) {
   base::i18n::BreakIterator iter(query, base::i18n::BreakIterator::BREAK_WORD);
   // TODO(evanm): support a locale here
   if (!iter.Init())
@@ -448,7 +450,7 @@ bool QueryParser::ParseQueryImpl(const string16& query, QueryNodeList* root) {
   return true;
 }
 
-void QueryParser::ExtractQueryWords(const string16& text,
+void QueryParser::ExtractQueryWords(const base::string16& text,
                                     std::vector<QueryWord>* words) {
   base::i18n::BreakIterator iter(text, base::i18n::BreakIterator::BREAK_WORD);
   // TODO(evanm): support a locale here
@@ -460,7 +462,7 @@ void QueryParser::ExtractQueryWords(const string16& text,
     // is not necessarily a word, but could also be a sequence of punctuation
     // or whitespace.
     if (iter.IsWord()) {
-      string16 word = iter.GetString();
+      base::string16 word = iter.GetString();
       if (!word.empty()) {
         words->push_back(QueryWord());
         words->back().word = word;
diff --git a/chrome/browser/history/query_parser.h b/chrome/browser/history/query_parser.h
index fe69e0b..02f40f6 100644
--- a/chrome/browser/history/query_parser.h
+++ b/chrome/browser/history/query_parser.h
@@ -16,7 +16,7 @@ class QueryNodeList;
 // Used by HasMatchIn.
 struct QueryWord {
   // The work to match against.
-  string16 word;
+  base::string16 word;
 
   // The starting position of the word in the original text.
   size_t position;
@@ -31,14 +31,14 @@ class QueryNode {
 
   // Serialize ourselves out to a string that can be passed to SQLite. Returns
   // the number of words in this node.
-  virtual int AppendToSQLiteQuery(string16* query) const = 0;
+  virtual int AppendToSQLiteQuery(base::string16* query) const = 0;
 
   // Return true if this is a QueryNodeWord, false if it's a QueryNodeList.
   virtual bool IsWord() const = 0;
 
   // Returns true if this node matches |word|. If |exact| is true, the string
   // must exactly match. Otherwise, this uses a starts with comparison.
-  virtual bool Matches(const string16& word, bool exact) const = 0;
+  virtual bool Matches(const base::string16& word, bool exact) const = 0;
 
   // Returns true if this node matches at least one of the words in |words|. An
   // entry is added to |match_positions| for all matching words giving the
@@ -50,7 +50,7 @@ class QueryNode {
   virtual bool HasMatchIn(const std::vector<QueryWord>& words) const = 0;
 
   // Appends the words that make up this node in |words|.
-  virtual void AppendWords(std::vector<string16>* words) const = 0;
+  virtual void AppendWords(std::vector<base::string16>* words) const = 0;
 };
 
 // This class is used to parse queries entered into the history search into more
@@ -66,27 +66,29 @@ class QueryParser {
   // point doing anything for them and we only adjust the minimum length
   // to 2 for Korean Hangul while using 3 for others. This is a temporary
   // hack until we have a segmentation support.
-  static bool IsWordLongEnoughForPrefixSearch(const string16& word);
+  static bool IsWordLongEnoughForPrefixSearch(const base::string16& word);
 
   // Parse a query into a SQLite query. The resulting query is placed in
   // |sqlite_query| and the number of words is returned.
-  int ParseQuery(const string16& query, string16* sqlite_query);
+  int ParseQuery(const base::string16& query, base::string16* sqlite_query);
 
   // Parses |query|, returning the words that make up it. Any words in quotes
   // are put in |words| without the quotes. For example, the query text
   // "foo bar" results in two entries being added to words, one for foo and one
   // for bar.
-  void ParseQueryWords(const string16& query, std::vector<string16>* words);
+  void ParseQueryWords(const base::string16& query,
+                       std::vector<string16>* words);
 
   // Parses |query|, returning the nodes that constitute the valid words in the
   // query. This is intended for later usage with DoesQueryMatch. Ownership of
   // the nodes passes to the caller.
-  void ParseQueryNodes(const string16& query, std::vector<QueryNode*>* nodes);
+  void ParseQueryNodes(const base::string16& query,
+                       std::vector<QueryNode*>* nodes);
 
   // Returns true if the string text matches the query nodes created by a call
   // to ParseQuery. If the query does match, each of the matching positions in
   // the text is added to |match_positions|.
-  bool DoesQueryMatch(const string16& text,
+  bool DoesQueryMatch(const base::string16& text,
                       const std::vector<QueryNode*>& nodes,
                       Snippet::MatchPositions* match_positions);
 
@@ -96,12 +98,13 @@ class QueryParser {
                       const std::vector<QueryNode*>& nodes);
 
   // Extracts the words from |text|, placing each word into |words|.
-  void ExtractQueryWords(const string16& text, std::vector<QueryWord>* words);
+  void ExtractQueryWords(const base::string16& text,
+                         std::vector<QueryWord>* words);
 
  private:
   // Does the work of parsing |query|; creates nodes in |root| as appropriate.
   // This is invoked from both of the ParseQuery methods.
-  bool ParseQueryImpl(const string16& query, QueryNodeList* root);
+  bool ParseQueryImpl(const base::string16& query, QueryNodeList* root);
 
   DISALLOW_COPY_AND_ASSIGN(QueryParser);
 };
diff --git a/chrome/browser/history/query_parser_unittest.cc b/chrome/browser/history/query_parser_unittest.cc
index 4982b30..ebc91e4 100644
--- a/chrome/browser/history/query_parser_unittest.cc
+++ b/chrome/browser/history/query_parser_unittest.cc
@@ -24,7 +24,7 @@ class QueryParserTest : public testing::Test {
 // Test helper: Convert a user query string in 8-bit (for hardcoding
 // convenience) to a SQLite query string.
 std::string QueryParserTest::QueryToString(const std::string& query) {
-  string16 sqlite_query;
+  base::string16 sqlite_query;
   query_parser_.ParseQuery(UTF8ToUTF16(query), &sqlite_query);
   return UTF16ToUTF8(sqlite_query);
 }
@@ -80,7 +80,7 @@ TEST_F(QueryParserTest, NumWords) {
   };
 
   for (size_t i = 0; i < arraysize(data); ++i) {
-    string16 query_string;
+    base::string16 query_string;
     EXPECT_EQ(data[i].expected_word_count,
               query_parser_.ParseQuery(UTF8ToUTF16(data[i].input),
                                        &query_string));
diff --git a/chrome/browser/history/scored_history_match.cc b/chrome/browser/history/scored_history_match.cc
index 3494d52..84ca61b 100644
--- a/chrome/browser/history/scored_history_match.cc
+++ b/chrome/browser/history/scored_history_match.cc
@@ -48,7 +48,7 @@ ScoredHistoryMatch::ScoredHistoryMatch()
 ScoredHistoryMatch::ScoredHistoryMatch(const URLRow& row,
                                        const VisitInfoVector& visits,
                                        const std::string& languages,
-                                       const string16& lower_string,
+                                       const base::string16& lower_string,
                                        const String16Vector& terms,
                                        const RowWordStarts& word_starts,
                                        const base::Time now,
@@ -64,12 +64,12 @@ ScoredHistoryMatch::ScoredHistoryMatch(const URLRow& row,
 
   // Figure out where each search term appears in the URL and/or page title
   // so that we can score as well as provide autocomplete highlighting.
-  string16 url = CleanUpUrlForMatching(gurl, languages);
-  string16 title = CleanUpTitleForMatching(row.title());
+  base::string16 url = CleanUpUrlForMatching(gurl, languages);
+  base::string16 title = CleanUpTitleForMatching(row.title());
   int term_num = 0;
   for (String16Vector::const_iterator iter = terms.begin(); iter != terms.end();
        ++iter, ++term_num) {
-    string16 term = *iter;
+    base::string16 term = *iter;
     TermMatches url_term_matches = MatchTermInString(term, url, term_num);
     TermMatches title_term_matches = MatchTermInString(term, title, term_num);
     if (url_term_matches.empty() && title_term_matches.empty())
@@ -134,7 +134,7 @@ ScoredHistoryMatch::ScoredHistoryMatch(const URLRow& row,
     // Now, the code that implements this.
     // The deepest prefix for this URL regardless of where the match is.
     const URLPrefix* best_prefix =
-        URLPrefix::BestURLPrefix(UTF8ToUTF16(gurl.spec()), string16());
+        URLPrefix::BestURLPrefix(UTF8ToUTF16(gurl.spec()), base::string16());
     DCHECK(best_prefix != NULL);
     const int num_components_in_best_prefix = best_prefix->num_components;
     // If the URL is inlineable, we must have a match.  Note the prefix that
@@ -276,7 +276,7 @@ TermMatches ScoredHistoryMatch::FilterTermMatchesByWordStarts(
 
 float ScoredHistoryMatch::GetTopicalityScore(
     const int num_terms,
-    const string16& url,
+    const base::string16& url,
     const RowWordStarts& word_starts) {
   // Because the below thread is not thread safe, we check that we're
   // only calling it from one thread: the UI thread.  Specifically,
diff --git a/chrome/browser/history/scored_history_match.h b/chrome/browser/history/scored_history_match.h
index 2e2af77..839459e 100644
--- a/chrome/browser/history/scored_history_match.h
+++ b/chrome/browser/history/scored_history_match.h
@@ -45,7 +45,7 @@ class ScoredHistoryMatch : public history::HistoryMatch {
   ScoredHistoryMatch(const URLRow& row,
                      const VisitInfoVector& visits,
                      const std::string& languages,
-                     const string16& lower_string,
+                     const base::string16& lower_string,
                      const String16Vector& terms_vector,
                      const RowWordStarts& word_starts,
                      const base::Time now,
@@ -91,7 +91,7 @@ class ScoredHistoryMatch : public history::HistoryMatch {
   // process so they only reflect matches used for scoring.  (For
   // instance, some mid-word matches are not given credit in scoring.)
   float GetTopicalityScore(const int num_terms,
-                           const string16& cleaned_up_url,
+                           const base::string16& cleaned_up_url,
                            const RowWordStarts& word_starts);
 
   // Precalculates raw_term_score_to_topicality_score_, used in
diff --git a/chrome/browser/history/scored_history_match_unittest.cc b/chrome/browser/history/scored_history_match_unittest.cc
index 2a22152..7f9a26e 100644
--- a/chrome/browser/history/scored_history_match_unittest.cc
+++ b/chrome/browser/history/scored_history_match_unittest.cc
@@ -51,9 +51,9 @@ class ScoredHistoryMatchTest : public testing::Test {
   // term match and word break information automatically that are needed
   // to call GetTopicalityScore().  It only works for scoring a single term,
   // not multiple terms.
-  float GetTopicalityScoreOfTermAgainstURLAndTitle(const string16& term,
-                                                   const string16& url,
-                                                   const string16& title);
+  float GetTopicalityScoreOfTermAgainstURLAndTitle(const base::string16& term,
+                                                   const base::string16& url,
+                                                   const base::string16& title);
 };
 
 URLRow ScoredHistoryMatchTest::MakeURLRow(const char* url,
@@ -93,9 +93,9 @@ String16Vector ScoredHistoryMatchTest::Make2Terms(const char* term_1,
 }
 
 float ScoredHistoryMatchTest::GetTopicalityScoreOfTermAgainstURLAndTitle(
-    const string16& term,
-    const string16& url,
-    const string16& title) {
+    const base::string16& term,
+    const base::string16& url,
+    const base::string16& title) {
   // Make an empty match and simply populate the fields we need in order
   // to call GetTopicalityScore().
   ScoredHistoryMatch scored_match;
@@ -361,9 +361,9 @@ TEST_F(ScoredHistoryMatchTest, GetTopicalityScoreTrailingSlash) {
 // This function only tests scoring of single terms that match exactly
 // once somewhere in the URL or title.
 TEST_F(ScoredHistoryMatchTest, GetTopicalityScore) {
-  string16 url = ASCIIToUTF16("http://abc.def.com/path1/path2?"
+  base::string16 url = ASCIIToUTF16("http://abc.def.com/path1/path2?"
       "arg1=val1&arg2=val2#hash_component");
-  string16 title = ASCIIToUTF16("here is a title");
+  base::string16 title = ASCIIToUTF16("here is a title");
   const float hostname_score =
       GetTopicalityScoreOfTermAgainstURLAndTitle(
           ASCIIToUTF16("abc"), url, title);
diff --git a/chrome/browser/history/shortcuts_backend.cc b/chrome/browser/history/shortcuts_backend.cc
index 3fba50e..a5abb3fe 100644
--- a/chrome/browser/history/shortcuts_backend.cc
+++ b/chrome/browser/history/shortcuts_backend.cc
@@ -82,15 +82,15 @@ ShortcutsBackend::Shortcut::MatchCore::MatchCore(
 }
 
 ShortcutsBackend::Shortcut::MatchCore::MatchCore(
-    const string16& fill_into_edit,
+    const base::string16& fill_into_edit,
     const GURL& destination_url,
-    const string16& contents,
+    const base::string16& contents,
     const ACMatchClassifications& contents_class,
-    const string16& description,
+    const base::string16& description,
     const ACMatchClassifications& description_class,
     content::PageTransition transition,
     AutocompleteMatch::Type type,
-    const string16& keyword)
+    const base::string16& keyword)
     : fill_into_edit(fill_into_edit),
       destination_url(destination_url),
       contents(contents),
@@ -124,7 +124,7 @@ AutocompleteMatch ShortcutsBackend::Shortcut::MatchCore::ToMatch() const {
 
 ShortcutsBackend::Shortcut::Shortcut(
     const std::string& id,
-    const string16& text,
+    const base::string16& text,
     const MatchCore& match_core,
     const base::Time& last_access_time,
     int number_of_hits)
@@ -189,9 +189,9 @@ void ShortcutsBackend::RemoveObserver(ShortcutsBackendObserver* obs) {
   observer_list_.RemoveObserver(obs);
 }
 
-void ShortcutsBackend::AddOrUpdateShortcut(const string16& text,
+void ShortcutsBackend::AddOrUpdateShortcut(const base::string16& text,
                                            const AutocompleteMatch& match) {
-  const string16 text_lowercase(base::i18n::ToLower(text));
+  const base::string16 text_lowercase(base::i18n::ToLower(text));
   const base::Time now(base::Time::Now());
   for (ShortcutMap::const_iterator it(
        shortcuts_map_.lower_bound(text_lowercase));
diff --git a/chrome/browser/history/shortcuts_backend.h b/chrome/browser/history/shortcuts_backend.h
index 242a0c6..a9c2e63 100644
--- a/chrome/browser/history/shortcuts_backend.h
+++ b/chrome/browser/history/shortcuts_backend.h
@@ -39,35 +39,35 @@ class ShortcutsBackend : public RefcountedBrowserContextKeyedService,
     // The pieces of an AutocompleteMatch that we preserve in a shortcut.
     struct MatchCore {
       explicit MatchCore(const AutocompleteMatch& match);
-      MatchCore(const string16& fill_into_edit,
+      MatchCore(const base::string16& fill_into_edit,
                 const GURL& destination_url,
-                const string16& contents,
+                const base::string16& contents,
                 const ACMatchClassifications& contents_class,
-                const string16& description,
+                const base::string16& description,
                 const ACMatchClassifications& description_class,
                 content::PageTransition transition,
                 AutocompleteMatch::Type type,
-                const string16& keyword);
+                const base::string16& keyword);
       ~MatchCore();
 
       AutocompleteMatch ToMatch() const;
 
-      string16 fill_into_edit;
+      base::string16 fill_into_edit;
       GURL destination_url;
-      string16 contents;
+      base::string16 contents;
       // For both contents_class and description_class, we strip MATCH
       // classifications; the ShortcutsProvider will re-mark MATCH regions based
       // on the user's current typing.
       ACMatchClassifications contents_class;
-      string16 description;
+      base::string16 description;
       ACMatchClassifications description_class;
       content::PageTransition transition;
       AutocompleteMatch::Type type;
-      string16 keyword;
+      base::string16 keyword;
     };
 
     Shortcut(const std::string& id,
-             const string16& text,
+             const base::string16& text,
              const MatchCore& match_core,
              const base::Time& last_access_time,
              int number_of_hits);
@@ -76,7 +76,7 @@ class ShortcutsBackend : public RefcountedBrowserContextKeyedService,
     ~Shortcut();
 
     std::string id;  // Unique guid for the shortcut.
-    string16 text;   // The user's original input string.
+    base::string16 text;   // The user's original input string.
     MatchCore match_core;
     base::Time last_access_time;  // Last time shortcut was selected.
     int number_of_hits;           // How many times shortcut was selected.
@@ -119,7 +119,7 @@ class ShortcutsBackend : public RefcountedBrowserContextKeyedService,
 
   // Looks for an existing shortcut to match.destination_url that starts with
   // |text|.  Updates that shortcut if found, otherwise adds a new shortcut.
-  void AddOrUpdateShortcut(const string16& text,
+  void AddOrUpdateShortcut(const base::string16& text,
                            const AutocompleteMatch& match);
 
  private:
diff --git a/chrome/browser/history/shortcuts_backend_unittest.cc b/chrome/browser/history/shortcuts_backend_unittest.cc
index 8f752e9..30abe74 100644
--- a/chrome/browser/history/shortcuts_backend_unittest.cc
+++ b/chrome/browser/history/shortcuts_backend_unittest.cc
@@ -25,7 +25,7 @@ namespace {
 
 AutocompleteMatch::Type ConvertedMatchType(AutocompleteMatch::Type type) {
   return ShortcutsBackend::Shortcut(
-      std::string(), string16(), ShortcutsBackend::Shortcut::MatchCore(
+      std::string(), base::string16(), ShortcutsBackend::Shortcut::MatchCore(
           AutocompleteMatch(NULL, 0, 0, type)),
       base::Time::Now(), 0).match_core.type;
 }
diff --git a/chrome/browser/history/snippet.cc b/chrome/browser/history/snippet.cc
index e1069a6..f73f56e 100644
--- a/chrome/browser/history/snippet.cc
+++ b/chrome/browser/history/snippet.cc
@@ -211,7 +211,7 @@ void Snippet::ComputeSnippet(const MatchPositions& match_positions,
   // The length of snippets we try to produce.
   // We can generate longer snippets but stop once we cross kSnippetMaxLength.
   const size_t kSnippetMaxLength = 200;
-  const string16 kEllipsis = ASCIIToUTF16(" ... ");
+  const base::string16 kEllipsis = ASCIIToUTF16(" ... ");
 
   UText* document_utext = NULL;
   UErrorCode status = U_ZERO_ERROR;
@@ -227,7 +227,7 @@ void Snippet::ComputeSnippet(const MatchPositions& match_positions,
   // We build the snippet by iterating through the matches and then grabbing
   // context around each match.  If matches are near enough each other (within
   // kSnippetContext), we skip the "..." between them.
-  string16 snippet;
+  base::string16 snippet;
   size_t start = 0;
   for (size_t i = 0; i < match_positions.size(); ++i) {
     // Some shorter names for the current match.
diff --git a/chrome/browser/history/snippet.h b/chrome/browser/history/snippet.h
index 058fbbd..9e6fdb0 100644
--- a/chrome/browser/history/snippet.h
+++ b/chrome/browser/history/snippet.h
@@ -52,7 +52,7 @@ class Snippet {
   void ComputeSnippet(const MatchPositions& matches,
                       const std::string& document);
 
-  const string16& text() const { return text_; }
+  const base::string16& text() const { return text_; }
   const MatchPositions& matches() const { return matches_; }
 
   // Efficiently swaps the contents of this snippet with the other.
@@ -60,7 +60,7 @@ class Snippet {
 
  private:
   // The text of the snippet.
-  string16 text_;
+  base::string16 text_;
 
   // The matches within text_.
   MatchPositions matches_;
diff --git a/chrome/browser/history/snippet_unittest.cc b/chrome/browser/history/snippet_unittest.cc
index 8f39d6d..e05836b 100644
--- a/chrome/browser/history/snippet_unittest.cc
+++ b/chrome/browser/history/snippet_unittest.cc
@@ -120,7 +120,7 @@ string16 BuildSnippet(const std::string& document,
   snippet.ComputeSnippet(match_positions, document);
 
   // Now "highlight" all matches in the snippet with **.
-  string16 star_snippet;
+  base::string16 star_snippet;
   Snippet::MatchPositions::const_iterator match;
   size_t pos = 0;
   for (match = snippet.matches().begin();
diff --git a/chrome/browser/history/top_sites_cache_unittest.cc b/chrome/browser/history/top_sites_cache_unittest.cc
index 947e7f6..89ee386 100644
--- a/chrome/browser/history/top_sites_cache_unittest.cc
+++ b/chrome/browser/history/top_sites_cache_unittest.cc
@@ -50,7 +50,7 @@ void TopSitesCacheTest::BuildTopSites(const char** spec, size_t size) {
       NOTREACHED() << "Duplicate URL found: " << spec_item;
     urls_seen.insert(spec_item);
     if (spec_item == spec[i]) {  // No indent: add new MostVisitedURL.
-      string16 title(ASCIIToUTF16("Title ") +
+      base::string16 title(ASCIIToUTF16("Title ") +
                      base::Uint64ToString16(top_sites_.size() + 1));
       top_sites_.push_back(MostVisitedURL(GURL(spec_item), title));
     }
diff --git a/chrome/browser/history/top_sites_impl_unittest.cc b/chrome/browser/history/top_sites_impl_unittest.cc
index dac6efe..8c6a253 100644
--- a/chrome/browser/history/top_sites_impl_unittest.cc
+++ b/chrome/browser/history/top_sites_impl_unittest.cc
@@ -243,7 +243,7 @@ class TopSitesImplTest : public HistoryUnitTestBase {
   }
 
   // Adds a page to history.
-  void AddPageToHistory(const GURL& url, const string16& title) {
+  void AddPageToHistory(const GURL& url, const base::string16& title) {
     RedirectList redirects;
     redirects.push_back(url);
     history_service()->AddPage(
@@ -255,7 +255,7 @@ class TopSitesImplTest : public HistoryUnitTestBase {
 
   // Adds a page to history.
   void AddPageToHistory(const GURL& url,
-                        const string16& title,
+                        const base::string16& title,
                         const history::RedirectList& redirects,
                         base::Time time) {
     history_service()->AddPage(
@@ -649,11 +649,11 @@ TEST_F(TopSitesImplTest, GetMostVisited) {
 TEST_F(TopSitesImplTest, SaveToDB) {
   MostVisitedURL url;
   GURL asdf_url("http://asdf.com");
-  string16 asdf_title(ASCIIToUTF16("ASDF"));
+  base::string16 asdf_title(ASCIIToUTF16("ASDF"));
   GURL google_url("http://google.com");
-  string16 google_title(ASCIIToUTF16("Google"));
+  base::string16 google_title(ASCIIToUTF16("Google"));
   GURL news_url("http://news.google.com");
-  string16 news_title(ASCIIToUTF16("Google News"));
+  base::string16 news_title(ASCIIToUTF16("Google News"));
 
   // Add asdf_url to history.
   AddPageToHistory(asdf_url, asdf_title);
@@ -713,11 +713,11 @@ TEST_F(TopSitesImplTest, SaveToDB) {
 TEST_F(TopSitesImplTest, SaveForcedToDB) {
   MostVisitedURL url;
   GURL asdf_url("http://asdf.com");
-  string16 asdf_title(ASCIIToUTF16("ASDF"));
+  base::string16 asdf_title(ASCIIToUTF16("ASDF"));
   GURL google_url("http://google.com");
-  string16 google_title(ASCIIToUTF16("Google"));
+  base::string16 google_title(ASCIIToUTF16("Google"));
   GURL news_url("http://news.google.com");
-  string16 news_title(ASCIIToUTF16("Google News"));
+  base::string16 news_title(ASCIIToUTF16("Google News"));
 
   // Add a number of forced URLs.
   std::vector<MostVisitedURL> list;
@@ -773,13 +773,13 @@ TEST_F(TopSitesImplTest, SaveForcedToDB) {
 TEST_F(TopSitesImplTest, RealDatabase) {
   MostVisitedURL url;
   GURL asdf_url("http://asdf.com");
-  string16 asdf_title(ASCIIToUTF16("ASDF"));
+  base::string16 asdf_title(ASCIIToUTF16("ASDF"));
   GURL google1_url("http://google.com");
   GURL google2_url("http://google.com/redirect");
   GURL google3_url("http://www.google.com");
-  string16 google_title(ASCIIToUTF16("Google"));
+  base::string16 google_title(ASCIIToUTF16("Google"));
   GURL news_url("http://news.google.com");
-  string16 news_title(ASCIIToUTF16("Google News"));
+  base::string16 news_title(ASCIIToUTF16("Google News"));
 
   url.url = asdf_url;
   url.title = asdf_title;
@@ -887,9 +887,9 @@ TEST_F(TopSitesImplTest, DeleteNotifications) {
   GURL google1_url("http://google.com");
   GURL google2_url("http://google.com/redirect");
   GURL google3_url("http://www.google.com");
-  string16 google_title(ASCIIToUTF16("Google"));
+  base::string16 google_title(ASCIIToUTF16("Google"));
   GURL news_url("http://news.google.com");
-  string16 news_title(ASCIIToUTF16("Google News"));
+  base::string16 news_title(ASCIIToUTF16("Google News"));
 
   AddPageToHistory(google1_url, google_title);
   AddPageToHistory(news_url, news_title);
diff --git a/chrome/browser/history/url_database.cc b/chrome/browser/history/url_database.cc
index 1c90cda..e1149b2 100644
--- a/chrome/browser/history/url_database.cc
+++ b/chrome/browser/history/url_database.cc
@@ -331,7 +331,7 @@ bool URLDatabase::FindShortestURLFromBase(const std::string& base,
   return true;
 }
 
-bool URLDatabase::GetTextMatches(const string16& query,
+bool URLDatabase::GetTextMatches(const base::string16& query,
                                  URLRows* results) {
   ScopedVector<QueryNode> query_nodes;
   query_parser_.ParseQueryNodes(query, &query_nodes.get());
@@ -342,19 +342,19 @@ bool URLDatabase::GetTextMatches(const string16& query,
 
   while (statement.Step()) {
     std::vector<QueryWord> query_words;
-    string16 url = base::i18n::ToLower(statement.ColumnString16(1));
+    base::string16 url = base::i18n::ToLower(statement.ColumnString16(1));
     query_parser_.ExtractQueryWords(url, &query_words);
     GURL gurl(url);
     if (gurl.is_valid()) {
       // Decode punycode to match IDN.
       // |query_words| won't be shown to user - therefore we can use empty
       // |languages| to reduce dependency (no need to call PrefService).
-      string16 ascii = base::ASCIIToUTF16(gurl.host());
-      string16 utf = net::IDNToUnicode(gurl.host(), std::string());
+      base::string16 ascii = base::ASCIIToUTF16(gurl.host());
+      base::string16 utf = net::IDNToUnicode(gurl.host(), std::string());
       if (ascii != utf)
         query_parser_.ExtractQueryWords(utf, &query_words);
     }
-    string16 title = base::i18n::ToLower(statement.ColumnString16(2));
+    base::string16 title = base::i18n::ToLower(statement.ColumnString16(2));
     query_parser_.ExtractQueryWords(title, &query_words);
 
     if (query_parser_.DoesQueryMatch(query_words, query_nodes.get())) {
@@ -411,7 +411,7 @@ bool URLDatabase::DropKeywordSearchTermsTable() {
 
 bool URLDatabase::SetKeywordSearchTermsForURL(URLID url_id,
                                               TemplateURLID keyword_id,
-                                              const string16& term) {
+                                              const base::string16& term) {
   DCHECK(url_id && keyword_id && !term.empty());
 
   sql::Statement exist_statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
@@ -455,7 +455,7 @@ bool URLDatabase::GetKeywordSearchTermRow(URLID url_id,
 }
 
 bool URLDatabase::GetKeywordSearchTermRows(
-    const string16& term,
+    const base::string16& term,
     std::vector<KeywordSearchTermRow>* rows) {
   sql::Statement statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
       "SELECT keyword_id, url_id FROM keyword_search_terms WHERE term=?"));
@@ -486,7 +486,7 @@ void URLDatabase::DeleteAllSearchTermsForKeyword(
 
 void URLDatabase::GetMostRecentKeywordSearchTerms(
     TemplateURLID keyword_id,
-    const string16& prefix,
+    const base::string16& prefix,
     int max_count,
     std::vector<KeywordSearchTermVisit>* matches) {
   // NOTE: the keyword_id can be zero if on first run the user does a query
@@ -504,9 +504,9 @@ void URLDatabase::GetMostRecentKeywordSearchTerms(
       "ORDER BY u.last_visit_time DESC LIMIT ?"));
 
   // NOTE: Keep this ToLower() call in sync with search_provider.cc.
-  string16 lower_prefix = base::i18n::ToLower(prefix);
+  base::string16 lower_prefix = base::i18n::ToLower(prefix);
   // This magic gives us a prefix search.
-  string16 next_prefix = lower_prefix;
+  base::string16 next_prefix = lower_prefix;
   next_prefix[next_prefix.size() - 1] =
       next_prefix[next_prefix.size() - 1] + 1;
   statement.BindInt64(0, keyword_id);
@@ -523,7 +523,7 @@ void URLDatabase::GetMostRecentKeywordSearchTerms(
   }
 }
 
-bool URLDatabase::DeleteKeywordSearchTerm(const string16& term) {
+bool URLDatabase::DeleteKeywordSearchTerm(const base::string16& term) {
   sql::Statement statement(GetDB().GetCachedStatement(SQL_FROM_HERE,
       "DELETE FROM keyword_search_terms WHERE term=?"));
   statement.BindString16(0, term);
diff --git a/chrome/browser/history/url_database.h b/chrome/browser/history/url_database.h
index 59b942a..a5ee0df 100644
--- a/chrome/browser/history/url_database.h
+++ b/chrome/browser/history/url_database.h
@@ -181,14 +181,14 @@ class URLDatabase {
 
   // Performs a brute force search over the database to find any URLs or titles
   // which match the |query| string.  Returns any matches in |results|.
-  bool GetTextMatches(const string16& query, URLRows* results);
+  bool GetTextMatches(const base::string16& query, URLRows* results);
 
   // Keyword Search Terms ------------------------------------------------------
 
   // Sets the search terms for the specified url/keyword pair.
   bool SetKeywordSearchTermsForURL(URLID url_id,
                                    TemplateURLID keyword_id,
-                                   const string16& term);
+                                   const base::string16& term);
 
   // Looks up a keyword search term given a url id. Returns all the search terms
   // in |rows|. Returns true on success.
@@ -196,7 +196,7 @@ class URLDatabase {
 
   // Looks up all keyword search terms given a term, Fills the rows with data.
   // Returns true on success and false otherwise.
-  bool GetKeywordSearchTermRows(const string16& term,
+  bool GetKeywordSearchTermRows(const base::string16& term,
                                 std::vector<KeywordSearchTermRow>* rows);
 
   // Deletes all search terms for the specified keyword that have been added by
@@ -207,12 +207,12 @@ class URLDatabase {
   // keyword.
   void GetMostRecentKeywordSearchTerms(
       TemplateURLID keyword_id,
-      const string16& prefix,
+      const base::string16& prefix,
       int max_count,
       std::vector<KeywordSearchTermVisit>* matches);
 
   // Deletes all searches matching |term|.
-  bool DeleteKeywordSearchTerm(const string16& term);
+  bool DeleteKeywordSearchTerm(const base::string16& term);
 
   // Deletes any search corresponding to |url_id|.
   bool DeleteKeywordSearchTermForURL(URLID url_id);
diff --git a/chrome/browser/history/url_database_unittest.cc b/chrome/browser/history/url_database_unittest.cc
index cfb0ec0..0f71dd4 100644
--- a/chrome/browser/history/url_database_unittest.cc
+++ b/chrome/browser/history/url_database_unittest.cc
@@ -134,7 +134,7 @@ TEST_F(URLDatabaseTest, KeywordSearchTermVisit) {
 
   // Add a keyword visit.
   TemplateURLID keyword_id = 100;
-  string16 keyword = UTF8ToUTF16("visit");
+  base::string16 keyword = UTF8ToUTF16("visit");
   ASSERT_TRUE(SetKeywordSearchTermsForURL(url_id, keyword_id, keyword));
 
   // Make sure we get it back.
@@ -233,7 +233,7 @@ TEST_F(URLDatabaseTest, GetAndDeleteKeywordSearchTermByTerm) {
 
   // Add a keyword visit.
   TemplateURLID keyword_id = 100;
-  string16 keyword = UTF8ToUTF16("visit");
+  base::string16 keyword = UTF8ToUTF16("visit");
   ASSERT_TRUE(SetKeywordSearchTermsForURL(url_id1, keyword_id, keyword));
 
   URLRow url_info2(GURL("https://www.google.com/"));
@@ -256,7 +256,7 @@ TEST_F(URLDatabaseTest, GetAndDeleteKeywordSearchTermByTerm) {
   url_info3.set_hidden(false);
   URLID url_id3 = AddURL(url_info3);
   ASSERT_NE(0, url_id3);
-  string16 keyword2 = UTF8ToUTF16("Search");
+  base::string16 keyword2 = UTF8ToUTF16("Search");
 
   ASSERT_TRUE(SetKeywordSearchTermsForURL(url_id3, keyword_id, keyword2));
 
diff --git a/chrome/browser/history/url_index_private_data.cc b/chrome/browser/history/url_index_private_data.cc
index b7d9c37..a17b0a4 100644
--- a/chrome/browser/history/url_index_private_data.cc
+++ b/chrome/browser/history/url_index_private_data.cc
@@ -73,7 +73,8 @@ typedef imui::InMemoryURLIndexCacheItem_WordStartsMapItem_WordStartsMapEntry
 // Algorithm Functions ---------------------------------------------------------
 
 // Comparison function for sorting search terms by descending length.
-bool LengthGreater(const string16& string_a, const string16& string_b) {
+bool LengthGreater(const base::string16& string_a,
+                   const base::string16& string_b) {
   return string_a.length() > string_b.length();
 }
 
@@ -151,14 +152,14 @@ URLIndexPrivateData::URLIndexPrivateData()
 }
 
 ScoredHistoryMatches URLIndexPrivateData::HistoryItemsForTerms(
-    string16 search_string,
+    base::string16 search_string,
     size_t cursor_position,
     const std::string& languages,
     BookmarkService* bookmark_service) {
   // If cursor position is set and useful (not at either end of the
   // string), allow the search string to be broken at cursor position.
   // We do this by pretending there's a space where the cursor is.
-  if ((cursor_position != string16::npos) &&
+  if ((cursor_position != base::string16::npos) &&
       (cursor_position < search_string.length()) &&
       (cursor_position > 0)) {
     search_string.insert(cursor_position, ASCIIToUTF16(" "));
@@ -170,8 +171,8 @@ ScoredHistoryMatches URLIndexPrivateData::HistoryItemsForTerms(
   // the index we need individual, lower-cased words, ignoring escapings. For
   // the final filtering we need whitespace separated substrings possibly
   // containing escaped characters.
-  string16 lower_raw_string(base::i18n::ToLower(search_string));
-  string16 lower_unescaped_string =
+  base::string16 lower_raw_string(base::i18n::ToLower(search_string));
+  base::string16 lower_unescaped_string =
       net::UnescapeURLComponent(lower_raw_string,
           net::UnescapeRule::SPACES | net::UnescapeRule::URL_SPECIAL_CHARS);
   // Extract individual 'words' (as opposed to 'terms'; see below) from the
@@ -527,7 +528,7 @@ HistoryIDSet URLIndexPrivateData::HistoryIDSetFromWords(
   std::sort(words.begin(), words.end(), LengthGreater);
   for (String16Vector::iterator iter = words.begin(); iter != words.end();
        ++iter) {
-    string16 uni_word = *iter;
+    base::string16 uni_word = *iter;
     HistoryIDSet term_history_set = HistoryIDsForTerm(uni_word);
     if (term_history_set.empty()) {
       history_id_set.clear();
@@ -548,7 +549,7 @@ HistoryIDSet URLIndexPrivateData::HistoryIDSetFromWords(
 }
 
 HistoryIDSet URLIndexPrivateData::HistoryIDsForTerm(
-    const string16& term) {
+    const base::string16& term) {
   if (term.empty())
     return HistoryIDSet();
 
@@ -572,7 +573,7 @@ HistoryIDSet URLIndexPrivateData::HistoryIDsForTerm(
     // If a prefix was found then determine the leftover characters to be used
     // for further refining the results from that prefix.
     Char16Set prefix_chars;
-    string16 leftovers(term);
+    base::string16 leftovers(term);
     if (best_prefix != search_term_cache_.end()) {
       // If the prefix is an exact match for the term then grab the cached
       // results and we're done.
@@ -624,7 +625,7 @@ HistoryIDSet URLIndexPrivateData::HistoryIDsForTerm(
     // contains words which do not have the search term as a proper subset.
     for (WordIDSet::iterator word_set_iter = word_id_set.begin();
          word_set_iter != word_id_set.end(); ) {
-      if (word_list_[*word_set_iter].find(term) == string16::npos)
+      if (word_list_[*word_set_iter].find(term) == base::string16::npos)
         word_id_set.erase(word_set_iter++);
       else
         ++word_set_iter;
@@ -706,7 +707,7 @@ bool URLIndexPrivateData::IndexRow(
 
   URLID row_id = row.id();
   // Strip out username and password before saving and indexing.
-  string16 url(net::FormatUrl(gurl, languages,
+  base::string16 url(net::FormatUrl(gurl, languages,
       net::kFormatUrlOmitUsernamePassword,
       net::UnescapeRule::NONE,
       NULL, NULL, NULL));
@@ -755,10 +756,10 @@ void URLIndexPrivateData::AddRowWordsToIndex(const URLRow& row,
   HistoryID history_id = static_cast<HistoryID>(row.id());
   // Split URL into individual, unique words then add in the title words.
   const GURL& gurl(row.url());
-  const string16& url = CleanUpUrlForMatching(gurl, languages);
+  const base::string16& url = CleanUpUrlForMatching(gurl, languages);
   String16Set url_words = String16SetFromString16(url,
       word_starts ? &word_starts->url_word_starts_ : NULL);
-  const string16& title = CleanUpTitleForMatching(row.title());
+  const base::string16& title = CleanUpTitleForMatching(row.title());
   String16Set title_words = String16SetFromString16(title,
       word_starts ? &word_starts->title_word_starts_ : NULL);
   String16Set words;
@@ -772,7 +773,7 @@ void URLIndexPrivateData::AddRowWordsToIndex(const URLRow& row,
   search_term_cache_.clear();  // Invalidate the term cache.
 }
 
-void URLIndexPrivateData::AddWordToIndex(const string16& term,
+void URLIndexPrivateData::AddWordToIndex(const base::string16& term,
                                          HistoryID history_id) {
   WordMap::iterator word_pos = word_map_.find(term);
   if (word_pos != word_map_.end())
@@ -781,7 +782,7 @@ void URLIndexPrivateData::AddWordToIndex(const string16& term,
     AddWordHistory(term, history_id);
 }
 
-void URLIndexPrivateData::AddWordHistory(const string16& term,
+void URLIndexPrivateData::AddWordHistory(const base::string16& term,
                                          HistoryID history_id) {
   WordID word_id = word_list_.size();
   if (available_words_.empty()) {
@@ -863,7 +864,7 @@ void URLIndexPrivateData::RemoveRowWordsFromIndex(const URLRow& row) {
       continue;  // The word is still in use.
 
     // The word is no longer in use. Reconcile any changes to character usage.
-    string16 word = word_list_[word_id];
+    base::string16 word = word_list_[word_id];
     Char16Set characters = Char16SetFromString16(word);
     for (Char16Set::iterator uni_char_iter = characters.begin();
          uni_char_iter != characters.end(); ++uni_char_iter) {
@@ -876,7 +877,7 @@ void URLIndexPrivateData::RemoveRowWordsFromIndex(const URLRow& row) {
     // Complete the removal of references to the word.
     word_id_history_map_.erase(word_id);
     word_map_.erase(word);
-    word_list_[word_id] = string16();
+    word_list_[word_id] = base::string16();
     available_words_.insert(word_id);
   }
 }
@@ -1180,7 +1181,7 @@ bool URLIndexPrivateData::RestoreHistoryInfoMap(
     url_row.set_typed_count(iter->typed_count());
     url_row.set_last_visit(base::Time::FromInternalValue(iter->last_visit()));
     if (iter->has_title()) {
-      string16 title(UTF8ToUTF16(iter->title()));
+      base::string16 title(UTF8ToUTF16(iter->title()));
       url_row.set_title(title);
     }
     history_info_map_[history_id].url_row = url_row;
@@ -1236,9 +1237,9 @@ bool URLIndexPrivateData::RestoreWordStartsMap(
          iter != history_info_map_.end(); ++iter) {
       RowWordStarts word_starts;
       const URLRow& row(iter->second.url_row);
-      const string16& url = CleanUpUrlForMatching(row.url(), languages);
+      const base::string16& url = CleanUpUrlForMatching(row.url(), languages);
       String16VectorFromString16(url, false, &word_starts.url_word_starts_);
-      const string16& title = CleanUpTitleForMatching(row.title());
+      const base::string16& title = CleanUpTitleForMatching(row.title());
       String16VectorFromString16(title, false, &word_starts.title_word_starts_);
       word_starts_map_[iter->first] = word_starts;
     }
@@ -1275,7 +1276,7 @@ URLIndexPrivateData::AddHistoryMatch::AddHistoryMatch(
     const URLIndexPrivateData& private_data,
     const std::string& languages,
     BookmarkService* bookmark_service,
-    const string16& lower_string,
+    const base::string16& lower_string,
     const String16Vector& lower_terms,
     const base::Time now)
   : private_data_(private_data),
diff --git a/chrome/browser/history/url_index_private_data.h b/chrome/browser/history/url_index_private_data.h
index e8db24b..6e26edf 100644
--- a/chrome/browser/history/url_index_private_data.h
+++ b/chrome/browser/history/url_index_private_data.h
@@ -48,11 +48,11 @@ class URLIndexPrivateData
  public:
   URLIndexPrivateData();
 
-  // Given a string16 in |term_string|, scans the history index and returns a
-  // vector with all scored, matching history items. The |term_string| is
-  // broken down into individual terms (words), each of which must occur in the
-  // candidate history item's URL or page title for the item to qualify;
-  // however, the terms do not necessarily have to be adjacent. We
+  // Given a base::string16 in |term_string|, scans the history index and
+  // returns a vector with all scored, matching history items. The
+  // |term_string| is broken down into individual terms (words), each of which
+  // must occur in the candidate history item's URL or page title for the item
+  // to qualify; however, the terms do not necessarily have to be adjacent. We
   // also allow breaking |term_string| at |cursor_position| (if
   // set). Once we have a set of candidates, they are filtered to ensure
   // that all |term_string| terms, as separated by whitespace and the
@@ -67,7 +67,7 @@ class URLIndexPrivateData
   // to this function. |bookmark_service| is used to boost a result's score if
   // its URL is referenced by one or more of the user's bookmarks.  |languages|
   // is used to help parse/format the URLs in the history index.
-  ScoredHistoryMatches HistoryItemsForTerms(string16 term_string,
+  ScoredHistoryMatches HistoryItemsForTerms(base::string16 term_string,
                                             size_t cursor_position,
                                             const std::string& languages,
                                             BookmarkService* bookmark_service);
@@ -189,7 +189,7 @@ class URLIndexPrivateData
     HistoryIDSet history_id_set_;
     bool used_;  // True if this item has been used for the current term search.
   };
-  typedef std::map<string16, SearchTermCacheItem> SearchTermCacheMap;
+  typedef std::map<base::string16, SearchTermCacheItem> SearchTermCacheMap;
 
   // A helper class which performs the final filter on each candidate
   // history URL match, inserting accepted matches into |scored_matches_|.
@@ -198,7 +198,7 @@ class URLIndexPrivateData
     AddHistoryMatch(const URLIndexPrivateData& private_data,
                     const std::string& languages,
                     BookmarkService* bookmark_service,
-                    const string16& lower_string,
+                    const base::string16& lower_string,
                     const String16Vector& lower_terms,
                     const base::Time now);
     ~AddHistoryMatch();
@@ -212,7 +212,7 @@ class URLIndexPrivateData
     const std::string& languages_;
     BookmarkService* bookmark_service_;
     ScoredHistoryMatches scored_matches_;
-    const string16& lower_string_;
+    const base::string16& lower_string_;
     const String16Vector& lower_terms_;
     const base::Time now_;
   };
@@ -239,7 +239,7 @@ class URLIndexPrivateData
 
   // Helper function to HistoryIDSetFromWords which composes a set of history
   // ids for the given term given in |term|.
-  HistoryIDSet HistoryIDsForTerm(const string16& term);
+  HistoryIDSet HistoryIDsForTerm(const base::string16& term);
 
   // Given a set of Char16s, finds words containing those characters.
   WordIDSet WordIDSetForTermChars(const Char16Set& term_chars);
@@ -270,11 +270,11 @@ class URLIndexPrivateData
 
   // Given a single word in |uni_word|, adds a reference for the containing
   // history item identified by |history_id| to the index.
-  void AddWordToIndex(const string16& uni_word, HistoryID history_id);
+  void AddWordToIndex(const base::string16& uni_word, HistoryID history_id);
 
   // Creates a new entry in the word/history map for |word_id| and add
   // |history_id| as the initial element of the word's set.
-  void AddWordHistory(const string16& uni_word, HistoryID history_id);
+  void AddWordHistory(const base::string16& uni_word, HistoryID history_id);
 
   // Updates an existing entry in the word/history index by adding the
   // |history_id| to set for |word_id| in the word_id_history_map_.
diff --git a/chrome/browser/history/web_history_service.cc b/chrome/browser/history/web_history_service.cc
index 3816713..a96fb25 100644
--- a/chrome/browser/history/web_history_service.cc
+++ b/chrome/browser/history/web_history_service.cc
@@ -233,7 +233,7 @@ std::string ServerTimeString(base::Time time) {
 // |options|. |version_info|, if not empty, should be a token that was received
 // from the server in response to a write operation. It is used to help ensure
 // read consistency after a write.
-GURL GetQueryUrl(const string16& text_query,
+GURL GetQueryUrl(const base::string16& text_query,
                  const QueryOptions& options,
                  const std::string& version_info) {
   GURL url = GURL(kHistoryQueryHistoryUrl);
@@ -299,7 +299,7 @@ WebHistoryService::~WebHistoryService() {
 }
 
 scoped_ptr<WebHistoryService::Request> WebHistoryService::QueryHistory(
-    const string16& text_query,
+    const base::string16& text_query,
     const QueryOptions& options,
     const WebHistoryService::QueryWebHistoryCallback& callback) {
   // Wrap the original callback into a generic completion callback.
diff --git a/chrome/browser/history/web_history_service.h b/chrome/browser/history/web_history_service.h
index 3a234a2..94dc680 100644
--- a/chrome/browser/history/web_history_service.h
+++ b/chrome/browser/history/web_history_service.h
@@ -59,7 +59,7 @@ class WebHistoryService : public BrowserContextKeyedService {
   // The caller takes ownership of the returned Request. If it is destroyed, the
   // request is cancelled.
   scoped_ptr<Request> QueryHistory(
-      const string16& text_query,
+      const base::string16& text_query,
       const QueryOptions& options,
       const QueryWebHistoryCallback& callback);
 
diff --git a/chrome/browser/infobars/confirm_infobar_delegate.cc b/chrome/browser/infobars/confirm_infobar_delegate.cc
index d7d1ac3..8739edf 100644
--- a/chrome/browser/infobars/confirm_infobar_delegate.cc
+++ b/chrome/browser/infobars/confirm_infobar_delegate.cc
@@ -37,7 +37,7 @@ bool ConfirmInfoBarDelegate::Cancel() {
 }
 
 string16 ConfirmInfoBarDelegate::GetLinkText() const {
-  return string16();
+  return base::string16();
 }
 
 bool ConfirmInfoBarDelegate::LinkClicked(WindowOpenDisposition disposition) {
diff --git a/chrome/browser/infobars/confirm_infobar_delegate.h b/chrome/browser/infobars/confirm_infobar_delegate.h
index 1dd7da0..ce90461 100644
--- a/chrome/browser/infobars/confirm_infobar_delegate.h
+++ b/chrome/browser/infobars/confirm_infobar_delegate.h
@@ -27,14 +27,14 @@ class ConfirmInfoBarDelegate : public InfoBarDelegate {
   virtual InfoBarAutomationType GetInfoBarAutomationType() const OVERRIDE;
 
   // Returns the message string to be displayed for the InfoBar.
-  virtual string16 GetMessageText() const = 0;
+  virtual base::string16 GetMessageText() const = 0;
 
   // Return the buttons to be shown for this InfoBar.
   virtual int GetButtons() const;
 
   // Return the label for the specified button. The default implementation
   // returns "OK" for the OK button and "Cancel" for the Cancel button.
-  virtual string16 GetButtonLabel(InfoBarButton button) const;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const;
 
   // Return whether or not the specified button needs elevation.
   virtual bool NeedElevation(InfoBarButton button) const;
@@ -51,7 +51,7 @@ class ConfirmInfoBarDelegate : public InfoBarDelegate {
 
   // Returns the text of the link to be displayed, if any. Otherwise returns
   // and empty string.
-  virtual string16 GetLinkText() const;
+  virtual base::string16 GetLinkText() const;
 
   // Called when the Link (if any) is clicked. The |disposition| specifies how
   // the resulting document should be loaded (based on the event flags present
diff --git a/chrome/browser/infobars/insecure_content_infobar_delegate.h b/chrome/browser/infobars/insecure_content_infobar_delegate.h
index 65d729f..139908f 100644
--- a/chrome/browser/infobars/insecure_content_infobar_delegate.h
+++ b/chrome/browser/infobars/insecure_content_infobar_delegate.h
@@ -42,11 +42,11 @@ class InsecureContentInfoBarDelegate : public ConfirmInfoBarDelegate {
   virtual void InfoBarDismissed() OVERRIDE;
   virtual InsecureContentInfoBarDelegate*
       AsInsecureContentInfoBarDelegate() OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
   virtual bool Accept() OVERRIDE;
   virtual bool Cancel() OVERRIDE;
-  virtual string16 GetLinkText() const OVERRIDE;
+  virtual base::string16 GetLinkText() const OVERRIDE;
   virtual bool LinkClicked(WindowOpenDisposition disposition) OVERRIDE;
 
   InfoBarType type_;
diff --git a/chrome/browser/infobars/simple_alert_infobar_delegate.cc b/chrome/browser/infobars/simple_alert_infobar_delegate.cc
index 0c092f2..8dc18d8 100644
--- a/chrome/browser/infobars/simple_alert_infobar_delegate.cc
+++ b/chrome/browser/infobars/simple_alert_infobar_delegate.cc
@@ -11,7 +11,7 @@
 // static
 void SimpleAlertInfoBarDelegate::Create(InfoBarService* infobar_service,
                                         int icon_id,
-                                        const string16& message,
+                                        const base::string16& message,
                                         bool auto_expire) {
   infobar_service->AddInfoBar(ConfirmInfoBarDelegate::CreateInfoBar(
       scoped_ptr<ConfirmInfoBarDelegate>(
@@ -20,7 +20,7 @@ void SimpleAlertInfoBarDelegate::Create(InfoBarService* infobar_service,
 
 SimpleAlertInfoBarDelegate::SimpleAlertInfoBarDelegate(
     int icon_id,
-    const string16& message,
+    const base::string16& message,
     bool auto_expire)
     : ConfirmInfoBarDelegate(),
       icon_id_(icon_id),
diff --git a/chrome/browser/infobars/simple_alert_infobar_delegate.h b/chrome/browser/infobars/simple_alert_infobar_delegate.h
index d2a1ed0..7bd125a 100644
--- a/chrome/browser/infobars/simple_alert_infobar_delegate.h
+++ b/chrome/browser/infobars/simple_alert_infobar_delegate.h
@@ -16,24 +16,24 @@ class SimpleAlertInfoBarDelegate : public ConfirmInfoBarDelegate {
   // |infobar_service|.
   static void Create(InfoBarService* infobar_service,
                      int icon_id,  // May be |kNoIconID| if no icon is shown.
-                     const string16& message,
+                     const base::string16& message,
                      bool auto_expire);
 
  private:
   SimpleAlertInfoBarDelegate(int icon_id,
-                             const string16& message,
+                             const base::string16& message,
                              bool auto_expire);
   virtual ~SimpleAlertInfoBarDelegate();
 
   // ConfirmInfoBarDelegate:
   virtual int GetIconID() const OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
   virtual int GetButtons() const OVERRIDE;
   virtual bool ShouldExpireInternal(
       const content::LoadCommittedDetails& details) const OVERRIDE;
 
   const int icon_id_;
-  string16 message_;
+  base::string16 message_;
   bool auto_expire_;  // Should it expire automatically on navigation?
 
   DISALLOW_COPY_AND_ASSIGN(SimpleAlertInfoBarDelegate);
diff --git a/chrome/browser/local_discovery/privet_notifications.cc b/chrome/browser/local_discovery/privet_notifications.cc
index a9aef82..31deebe 100644
--- a/chrome/browser/local_discovery/privet_notifications.cc
+++ b/chrome/browser/local_discovery/privet_notifications.cc
@@ -234,7 +234,7 @@ bool PrivetNotificationService::IsForced() {
 
 void PrivetNotificationService::PrivetNotify(bool has_multiple,
                                              bool added) {
-    string16 product_name = l10n_util::GetStringUTF16(
+    base::string16 product_name = l10n_util::GetStringUTF16(
         IDS_LOCAL_DISOCVERY_PRODUCT_NAME_PRINTER);
 
     int title_resource = has_multiple ?
@@ -245,8 +245,9 @@ void PrivetNotificationService::PrivetNotify(bool has_multiple,
         IDS_LOCAL_DISOCVERY_NOTIFICATION_CONTENTS_PRINTER_MULTIPLE :
         IDS_LOCAL_DISOCVERY_NOTIFICATION_CONTENTS_PRINTER;
 
-    string16 title = l10n_util::GetStringUTF16(title_resource);
-    string16 body = l10n_util::GetStringFUTF16(body_resource, product_name);
+    base::string16 title = l10n_util::GetStringUTF16(title_resource);
+    base::string16 body =
+        l10n_util::GetStringFUTF16(body_resource, product_name);
 
     Profile* profile_object = Profile::FromBrowserContext(profile_);
     message_center::RichNotificationData rich_notification_data;
diff --git a/chrome/browser/media_galleries/fileapi/picasa_finder.cc b/chrome/browser/media_galleries/fileapi/picasa_finder.cc
index 87ec630..68f2c79 100644
--- a/chrome/browser/media_galleries/fileapi/picasa_finder.cc
+++ b/chrome/browser/media_galleries/fileapi/picasa_finder.cc
@@ -39,7 +39,7 @@ base::FilePath GetCustomPicasaAppDataPathFromWinRegistry() {
     return base::FilePath();
   }
 
-  string16 value;
+  base::string16 value;
   if (key.ReadValue(kPicasaRegistryAppDataPathKey, &value) != ERROR_SUCCESS)
     return base::FilePath();
   if (value.empty())
diff --git a/chrome/browser/media_galleries/media_file_system_registry.cc b/chrome/browser/media_galleries/media_file_system_registry.cc
index eef446c..af27d95 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry.cc
@@ -182,7 +182,7 @@ class RPHReferenceManager : public content::NotificationObserver {
 
 }  // namespace
 
-MediaFileSystemInfo::MediaFileSystemInfo(const string16& fs_name,
+MediaFileSystemInfo::MediaFileSystemInfo(const base::string16& fs_name,
                                          const base::FilePath& fs_path,
                                          const std::string& filesystem_id,
                                          MediaGalleryPrefId pref_id,
diff --git a/chrome/browser/media_galleries/media_file_system_registry.h b/chrome/browser/media_galleries/media_file_system_registry.h
index d47a490..b79fc0d 100644
--- a/chrome/browser/media_galleries/media_file_system_registry.h
+++ b/chrome/browser/media_galleries/media_file_system_registry.h
@@ -41,7 +41,7 @@ class IsolatedContext;
 // client, including metadata like the name and ID, and API handles like the
 // fsid (filesystem ID) used to hook up the API objects.
 struct MediaFileSystemInfo {
-  MediaFileSystemInfo(const string16& fs_name,
+  MediaFileSystemInfo(const base::string16& fs_name,
                       const base::FilePath& fs_path,
                       const std::string& filesystem_id,
                       MediaGalleryPrefId pref_id,
@@ -51,7 +51,7 @@ struct MediaFileSystemInfo {
   MediaFileSystemInfo();
   ~MediaFileSystemInfo();
 
-  string16 name;
+  base::string16 name;
   base::FilePath path;
   std::string fsid;
   MediaGalleryPrefId pref_id;
diff --git a/chrome/browser/media_galleries/media_file_system_registry_unittest.cc b/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
index 6ede692..b98ac8b 100644
--- a/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
+++ b/chrome/browser/media_galleries/media_file_system_registry_unittest.cc
@@ -227,12 +227,12 @@ class ProfileState {
   extensions::Extension* regular_permission_extension();
   Profile* profile();
 
-  void AddNameForReadCompare(const string16& name);
-  void AddNameForAllCompare(const string16& name);
+  void AddNameForReadCompare(const base::string16& name);
+  void AddNameForAllCompare(const base::string16& name);
 
  private:
   void CompareResults(const std::string& test,
-                      const std::vector<string16>& names,
+                      const std::vector<base::string16>& names,
                       const std::vector<MediaFileSystemInfo>& expected,
                       const std::vector<MediaFileSystemInfo>& actual);
   bool ContainsEntry(const MediaFileSystemInfo& info,
@@ -257,8 +257,8 @@ class ProfileState {
   content::MockRenderProcessHost* single_rph_;
   content::MockRenderProcessHost* shared_rph_;
 
-  std::vector<string16> compare_names_read_;
-  std::vector<string16> compare_names_all_;
+  std::vector<base::string16> compare_names_read_;
+  std::vector<base::string16> compare_names_all_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfileState);
 };
@@ -317,9 +317,10 @@ class MediaFileSystemRegistryTest : public ChromeRenderViewHostTestHarness {
       ProfileState* profile_state);
 
   void ProcessAttach(const std::string& id,
-                     const string16& name,
+                     const base::string16& name,
                      const base::FilePath::StringType& location) {
-    StorageInfo info(id, string16(), location, name, string16(), string16(), 0);
+    StorageInfo info(id, base::string16(), location, name, base::string16(),
+                     base::string16(), 0);
     StorageMonitor::GetInstance()->receiver()->ProcessAttach(info);
   }
 
@@ -479,7 +480,7 @@ void ProfileState::CheckGalleries(
 
   // No Media Galleries permissions.
   std::vector<MediaFileSystemInfo> empty_expectation;
-  std::vector<string16> empty_names;
+  std::vector<base::string16> empty_names;
   registry->GetMediaFileSystemsForExtension(
       rvh, no_permissions_extension_.get(),
       base::Bind(&ProfileState::CompareResults, base::Unretained(this),
@@ -534,11 +535,11 @@ Profile* ProfileState::profile() {
   return profile_.get();
 }
 
-void ProfileState::AddNameForReadCompare(const string16& name) {
+void ProfileState::AddNameForReadCompare(const base::string16& name) {
   compare_names_read_.push_back(name);
 }
 
-void ProfileState::AddNameForAllCompare(const string16& name) {
+void ProfileState::AddNameForAllCompare(const base::string16& name) {
   compare_names_all_.push_back(name);
 }
 
@@ -558,7 +559,7 @@ bool ProfileState::ContainsEntry(
 
 void ProfileState::CompareResults(
     const std::string& test,
-    const std::vector<string16>& names,
+    const std::vector<base::string16>& names,
     const std::vector<MediaFileSystemInfo>& expected,
     const std::vector<MediaFileSystemInfo>& actual) {
   num_comparisons_++;
@@ -569,7 +570,7 @@ void ProfileState::CompareResults(
   std::sort(sorted.begin(), sorted.end(), MediaFileSystemInfoComparator);
   std::vector<MediaFileSystemInfo> expect(expected);
   std::sort(expect.begin(), expect.end(), MediaFileSystemInfoComparator);
-  std::vector<string16> expect_names(names);
+  std::vector<base::string16> expect_names(names);
   std::sort(expect_names.begin(), expect_names.end());
 
   for (size_t i = 0; i < expect.size() && i < sorted.size(); ++i) {
@@ -621,7 +622,8 @@ std::string MediaFileSystemRegistryTest::AddUserGallery(
   for (size_t i = 0; i < profile_states_.size(); ++i) {
     profile_states_[i]->GetMediaGalleriesPrefs()->AddGallery(
         device_id, base::FilePath(), true /*user_added*/,
-        string16(), string16(), string16(), 0, base::Time::Now());
+        base::string16(), base::string16(), base::string16(), 0,
+        base::Time::Now());
   }
   return device_id;
 }
@@ -632,7 +634,7 @@ std::string MediaFileSystemRegistryTest::AttachDevice(
     const base::FilePath& location) {
   std::string device_id = StorageInfo::MakeDeviceId(type, unique_id);
   DCHECK(StorageInfo::IsRemovableDevice(device_id));
-  string16 label = location.BaseName().LossyDisplayName();
+  base::string16 label = location.BaseName().LossyDisplayName();
   ProcessAttach(device_id, label, location.value());
   base::MessageLoop::current()->RunUntilIdle();
   return device_id;
diff --git a/chrome/browser/media_galleries/media_galleries_dialog_controller.h b/chrome/browser/media_galleries/media_galleries_dialog_controller.h
index 6221dd2..a567315 100644
--- a/chrome/browser/media_galleries/media_galleries_dialog_controller.h
+++ b/chrome/browser/media_galleries/media_galleries_dialog_controller.h
@@ -70,13 +70,13 @@ class MediaGalleriesDialogController
                                  const base::Closure& on_finish);
 
   // The title of the dialog view.
-  string16 GetHeader() const;
+  base::string16 GetHeader() const;
 
   // Explanatory text directly below the title.
-  string16 GetSubtext() const;
+  base::string16 GetSubtext() const;
 
   // Header for unattached devices part of the dialog.
-  string16 GetUnattachedLocationsHeader() const;
+  base::string16 GetUnattachedLocationsHeader() const;
 
   // Initial state of whether the dialog's confirmation button will be enabled.
   bool HasPermittedGalleries() const;
diff --git a/chrome/browser/media_galleries/media_galleries_dialog_controller_mock.h b/chrome/browser/media_galleries/media_galleries_dialog_controller_mock.h
index 4457938..4d5b211 100644
--- a/chrome/browser/media_galleries/media_galleries_dialog_controller_mock.h
+++ b/chrome/browser/media_galleries/media_galleries_dialog_controller_mock.h
@@ -15,8 +15,8 @@ class MediaGalleriesDialogControllerMock
       const extensions::Extension& extension);
   virtual ~MediaGalleriesDialogControllerMock();
 
-  MOCK_CONST_METHOD0(GetHeader, string16());
-  MOCK_CONST_METHOD0(GetSubtext, string16());
+  MOCK_CONST_METHOD0(GetHeader, base::string16());
+  MOCK_CONST_METHOD0(GetSubtext, base::string16());
   MOCK_CONST_METHOD0(HasPermittedGalleries, bool());
   MOCK_CONST_METHOD0(AttachedPermissions, GalleryPermissionsVector());
   MOCK_CONST_METHOD0(UnattachedPermissions, GalleryPermissionsVector());
diff --git a/chrome/browser/media_galleries/media_galleries_dialog_controller_unittest.cc b/chrome/browser/media_galleries/media_galleries_dialog_controller_unittest.cc
index 9f43cef..94b7645 100644
--- a/chrome/browser/media_galleries/media_galleries_dialog_controller_unittest.cc
+++ b/chrome/browser/media_galleries/media_galleries_dialog_controller_unittest.cc
@@ -13,7 +13,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 std::string GalleryName(const MediaGalleryPrefInfo& gallery) {
-  string16 name = gallery.GetGalleryDisplayName();
+  base::string16 name = gallery.GetGalleryDisplayName();
   return UTF16ToASCII(name);
 }
 
@@ -33,7 +33,7 @@ TEST(MediaGalleriesDialogControllerTest, TestNameGeneration) {
   gallery.display_name = ASCIIToUTF16("override");
   EXPECT_EQ("override", GalleryName(gallery));
 
-  gallery.display_name = string16();
+  gallery.display_name = base::string16();
   gallery.volume_label = ASCIIToUTF16("label");
   EXPECT_EQ(galleryName, GalleryName(gallery));
 
@@ -60,10 +60,10 @@ TEST(MediaGalleriesDialogControllerTest, TestNameGeneration) {
   gallery.model_name = ASCIIToUTF16("model");
   EXPECT_EQ("override", GalleryName(gallery));
 
-  gallery.display_name = string16();
+  gallery.display_name = base::string16();
   EXPECT_EQ("volume", GalleryName(gallery));
 
-  gallery.volume_label = string16();
+  gallery.volume_label = base::string16();
   EXPECT_EQ("vendor, model", GalleryName(gallery));
 
   gallery.total_size_in_bytes = 1000000;
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.cc b/chrome/browser/media_galleries/media_galleries_preferences.cc
index fffa94a..45a7f3e 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.cc
+++ b/chrome/browser/media_galleries/media_galleries_preferences.cc
@@ -127,13 +127,13 @@ bool GetType(const DictionaryValue& dict, MediaGalleryPrefInfo::Type* type) {
 bool PopulateGalleryPrefInfoFromDictionary(
     const DictionaryValue& dict, MediaGalleryPrefInfo* out_gallery_info) {
   MediaGalleryPrefId pref_id;
-  string16 display_name;
+  base::string16 display_name;
   std::string device_id;
   base::FilePath::StringType path;
   MediaGalleryPrefInfo::Type type = MediaGalleryPrefInfo::kAutoDetected;
-  string16 volume_label;
-  string16 vendor_name;
-  string16 model_name;
+  base::string16 volume_label;
+  base::string16 vendor_name;
+  base::string16 model_name;
   double total_size_in_bytes = 0.0;
   double last_attach_time = 0.0;
   bool volume_metadata_valid = false;
@@ -245,8 +245,8 @@ bool GetMediaGalleryPermissionFromDictionary(
   return false;
 }
 
-string16 GetDisplayNameForDevice(uint64 storage_size_in_bytes,
-                                 const string16& name) {
+base::string16 GetDisplayNameForDevice(uint64 storage_size_in_bytes,
+                                       const base::string16& name) {
   DCHECK(!name.empty());
   return (storage_size_in_bytes == 0) ?
       name : ui::FormatBytes(storage_size_in_bytes) + ASCIIToUTF16(" ") + name;
@@ -254,8 +254,8 @@ string16 GetDisplayNameForDevice(uint64 storage_size_in_bytes,
 
 // For a device with |device_name| and a relative path |sub_folder|, construct
 // a display name. If |sub_folder| is empty, then just return |device_name|.
-string16 GetDisplayNameForSubFolder(const string16& device_name,
-                                    const base::FilePath& sub_folder) {
+base::string16 GetDisplayNameForSubFolder(const base::string16& device_name,
+                                          const base::FilePath& sub_folder) {
   if (sub_folder.empty())
     return device_name;
   return (sub_folder.BaseName().LossyDisplayName() +
@@ -263,12 +263,12 @@ string16 GetDisplayNameForSubFolder(const string16& device_name,
           device_name);
 }
 
-string16 GetFullProductName(const string16& vendor_name,
-                            const string16& model_name) {
+base::string16 GetFullProductName(const base::string16& vendor_name,
+                                  const base::string16& model_name) {
   if (vendor_name.empty() && model_name.empty())
-    return string16();
+    return base::string16();
 
-  string16 product_name;
+  base::string16 product_name;
   if (vendor_name.empty())
     product_name = model_name;
   else if (model_name.empty())
@@ -297,7 +297,7 @@ base::FilePath MediaGalleryPrefInfo::AbsolutePath() const {
   return base_path.empty() ? base_path : base_path.Append(path);
 }
 
-string16 MediaGalleryPrefInfo::GetGalleryDisplayName() const {
+base::string16 MediaGalleryPrefInfo::GetGalleryDisplayName() const {
   if (!StorageInfo::IsRemovableDevice(device_id)) {
     // For fixed storage, the default name is the fully qualified directory
     // name, or in the case of a root directory, the root directory name.
@@ -322,7 +322,7 @@ string16 MediaGalleryPrefInfo::GetGalleryDisplayName() const {
 #endif
   }
 
-  string16 name = display_name;
+  base::string16 name = display_name;
   if (name.empty())
     name = volume_label;
   if (name.empty())
@@ -338,12 +338,12 @@ string16 MediaGalleryPrefInfo::GetGalleryDisplayName() const {
   return name;
 }
 
-string16 MediaGalleryPrefInfo::GetGalleryTooltip() const {
+base::string16 MediaGalleryPrefInfo::GetGalleryTooltip() const {
   return AbsolutePath().LossyDisplayName();
 }
 
-string16 MediaGalleryPrefInfo::GetGalleryAdditionalDetails() const {
-  string16 attached;
+base::string16 MediaGalleryPrefInfo::GetGalleryAdditionalDetails() const {
+  base::string16 attached;
   if (StorageInfo::IsRemovableDevice(device_id)) {
     if (MediaStorageUtil::IsRemovableStorageAttached(device_id)) {
       attached = l10n_util::GetStringUTF16(
@@ -562,7 +562,7 @@ void MediaGalleriesPreferences::OnFinderDeviceID(const std::string& device_id) {
 
     AddGalleryInternal(device_id, ASCIIToUTF16(gallery_name),
                        base::FilePath(), false /*not user added*/,
-                       string16(), string16(), string16(), 0,
+                       base::string16(), base::string16(), base::string16(), 0,
                        base::Time(), false, 2);
   }
 
@@ -698,20 +698,20 @@ base::FilePath MediaGalleriesPreferences::LookUpGalleryPathForExtension(
 MediaGalleryPrefId MediaGalleriesPreferences::AddGallery(
     const std::string& device_id,
     const base::FilePath& relative_path, bool user_added,
-    const string16& volume_label, const string16& vendor_name,
-    const string16& model_name, uint64 total_size_in_bytes,
+    const base::string16& volume_label, const base::string16& vendor_name,
+    const base::string16& model_name, uint64 total_size_in_bytes,
     base::Time last_attach_time) {
   DCHECK(IsInitialized());
-  return AddGalleryInternal(device_id, string16(), relative_path, user_added,
-                            volume_label, vendor_name, model_name,
+  return AddGalleryInternal(device_id, base::string16(), relative_path,
+                            user_added, volume_label, vendor_name, model_name,
                             total_size_in_bytes, last_attach_time, true, 2);
 }
 
 MediaGalleryPrefId MediaGalleriesPreferences::AddGalleryInternal(
-    const std::string& device_id, const string16& display_name,
+    const std::string& device_id, const base::string16& display_name,
     const base::FilePath& relative_path, bool user_added,
-    const string16& volume_label, const string16& vendor_name,
-    const string16& model_name, uint64 total_size_in_bytes,
+    const base::string16& volume_label, const base::string16& vendor_name,
+    const base::string16& model_name, uint64 total_size_in_bytes,
     base::Time last_attach_time,
     bool volume_metadata_valid,
     int prefs_version) {
diff --git a/chrome/browser/media_galleries/media_galleries_preferences.h b/chrome/browser/media_galleries/media_galleries_preferences.h
index 070e4be..8f2e939 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences.h
+++ b/chrome/browser/media_galleries/media_galleries_preferences.h
@@ -60,7 +60,7 @@ struct MediaGalleryPrefInfo {
   MediaGalleryPrefId pref_id;
 
   // The user-visible name of this gallery.
-  string16 display_name;
+  base::string16 display_name;
 
   // A string which uniquely and persistently identifies the device that the
   // gallery lives on.
@@ -74,15 +74,15 @@ struct MediaGalleryPrefInfo {
 
   // The volume label of the volume/device on which the gallery
   // resides. Empty if there is no such label or it is unknown.
-  string16 volume_label;
+  base::string16 volume_label;
 
   // Vendor name for the volume/device on which the gallery is located.
   // Will be empty if unknown.
-  string16 vendor_name;
+  base::string16 vendor_name;
 
   // Model name for the volume/device on which the gallery is located.
   // Will be empty if unknown.
-  string16 model_name;
+  base::string16 model_name;
 
   // The capacity in bytes of the volume/device on which the gallery is
   // located. Will be zero if unknown.
@@ -104,9 +104,9 @@ struct MediaGalleryPrefInfo {
   int prefs_version;
 
   // Called by views to provide details for the gallery permission entries.
-  string16 GetGalleryDisplayName() const;
-  string16 GetGalleryTooltip() const;
-  string16 GetGalleryAdditionalDetails() const;
+  base::string16 GetGalleryDisplayName() const;
+  base::string16 GetGalleryTooltip() const;
+  base::string16 GetGalleryAdditionalDetails() const;
 
   // Returns true if the gallery is currently a removable device gallery which
   // is now attached, or a fixed storage gallery.
@@ -195,9 +195,9 @@ class MediaGalleriesPreferences : public BrowserContextKeyedService,
   MediaGalleryPrefId AddGallery(const std::string& device_id,
                                 const base::FilePath& relative_path,
                                 bool user_added,
-                                const string16& volume_label,
-                                const string16& vendor_name,
-                                const string16& model_name,
+                                const base::string16& volume_label,
+                                const base::string16& vendor_name,
+                                const base::string16& model_name,
                                 uint64 total_size_in_bytes,
                                 base::Time last_attach_time);
 
@@ -263,12 +263,12 @@ class MediaGalleriesPreferences : public BrowserContextKeyedService,
   void InitFromPrefs();
 
   MediaGalleryPrefId AddGalleryInternal(const std::string& device_id,
-                                        const string16& display_name,
+                                        const base::string16& display_name,
                                         const base::FilePath& relative_path,
                                         bool user_added,
-                                        const string16& volume_label,
-                                        const string16& vendor_name,
-                                        const string16& model_name,
+                                        const base::string16& volume_label,
+                                        const base::string16& vendor_name,
+                                        const base::string16& model_name,
                                         uint64 total_size_in_bytes,
                                         base::Time last_attach_time,
                                         bool volume_metadata_valid,
diff --git a/chrome/browser/media_galleries/media_galleries_preferences_unittest.cc b/chrome/browser/media_galleries/media_galleries_preferences_unittest.cc
index bbcab9e..45d1b5e 100644
--- a/chrome/browser/media_galleries/media_galleries_preferences_unittest.cc
+++ b/chrome/browser/media_galleries/media_galleries_preferences_unittest.cc
@@ -200,7 +200,7 @@ class MediaGalleriesPreferencesTest : public testing::Test {
     return default_galleries_count_;
   }
 
-  void AddGalleryExpectation(MediaGalleryPrefId id, string16 display_name,
+  void AddGalleryExpectation(MediaGalleryPrefId id, base::string16 display_name,
                              std::string device_id,
                              base::FilePath relative_path,
                              MediaGalleryPrefInfo::Type type) {
@@ -217,30 +217,33 @@ class MediaGalleriesPreferencesTest : public testing::Test {
   }
 
   MediaGalleryPrefId AddGalleryWithNameV0(const std::string& device_id,
-                                          const string16& display_name,
+                                          const base::string16& display_name,
                                           const base::FilePath& relative_path,
                                           bool user_added) {
     return gallery_prefs()->AddGalleryInternal(
         device_id, display_name, relative_path, user_added,
-        string16(), string16(), string16(), 0, base::Time(), false, 0);
+        base::string16(), base::string16(), base::string16(), 0, base::Time(),
+        false, 0);
   }
 
   MediaGalleryPrefId AddGalleryWithNameV1(const std::string& device_id,
-                                          const string16& display_name,
+                                          const base::string16& display_name,
                                           const base::FilePath& relative_path,
                                           bool user_added) {
     return gallery_prefs()->AddGalleryInternal(
         device_id, display_name, relative_path, user_added,
-        string16(), string16(), string16(), 0, base::Time(), false, 1);
+        base::string16(), base::string16(), base::string16(), 0, base::Time(),
+        false, 1);
   }
 
   MediaGalleryPrefId AddGalleryWithNameV2(const std::string& device_id,
-                                          const string16& display_name,
+                                          const base::string16& display_name,
                                           const base::FilePath& relative_path,
                                           bool user_added) {
     return gallery_prefs()->AddGalleryInternal(
         device_id, display_name, relative_path, user_added,
-        string16(), string16(), string16(), 0, base::Time(), false, 2);
+        base::string16(), base::string16(), base::string16(), 0, base::Time(),
+        false, 2);
   }
 
   bool UpdateDeviceIDForSingletonType(const std::string& device_id) {
@@ -382,7 +385,7 @@ TEST_F(MediaGalleriesPreferencesTest, AddGalleryWithVolumeMetadata) {
                                    ASCIIToUTF16("model name"),
                                    1000000ULL, now);
   EXPECT_EQ(default_galleries_count() + 1UL, id);
-  AddGalleryExpectation(id, string16(), info.device_id(), relative_path,
+  AddGalleryExpectation(id, base::string16(), info.device_id(), relative_path,
                         MediaGalleryPrefInfo::kAutoDetected);
   Verify();
 
@@ -428,7 +431,7 @@ TEST_F(MediaGalleriesPreferencesTest, ReplaceGalleryWithVolumeMetadata) {
                                             ASCIIToUTF16("model name"),
                                             1000000ULL, now);
   EXPECT_EQ(id, metadata_id);
-  AddGalleryExpectation(id, string16(), info.device_id(), relative_path,
+  AddGalleryExpectation(id, base::string16(), info.device_id(), relative_path,
                         MediaGalleryPrefInfo::kAutoDetected);
 
   // Make sure the display_name is set to empty now, as the metadata
@@ -502,7 +505,7 @@ TEST_F(MediaGalleriesPreferencesTest, UpdateGalleryNameV2) {
   Verify();
 
   // Won't override the name -- don't change any expectation.
-  info.set_name(string16());
+  info.set_name(base::string16());
   AddGalleryWithNameV2(info.device_id(), info.name(), relative_path, false);
   Verify();
 
@@ -864,9 +867,9 @@ TEST(MediaGalleryPrefInfoTest, NameGeneration) {
   info.model_name = ASCIIToUTF16("model");
   EXPECT_EQ(ASCIIToUTF16("o2"), info.GetGalleryDisplayName());
 
-  info.display_name = string16();
+  info.display_name = base::string16();
   EXPECT_EQ(ASCIIToUTF16("vol"), info.GetGalleryDisplayName());
-  info.volume_label = string16();
+  info.volume_label = base::string16();
   EXPECT_EQ(ASCIIToUTF16("vendor, model"), info.GetGalleryDisplayName());
 
   info.device_id = StorageInfo::MakeDeviceId(
diff --git a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.cc b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.cc
index 1119a17e..c2e1e52 100644
--- a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.cc
@@ -36,14 +36,14 @@ namespace {
 // Gets the details of the MTP partition storage specified by the
 // |storage_path| on the UI thread. Returns true if the storage details are
 // valid and returns false otherwise.
-bool GetStorageInfoOnUIThread(const string16& storage_path,
-                              string16* pnp_device_id,
-                              string16* storage_object_id) {
+bool GetStorageInfoOnUIThread(const base::string16& storage_path,
+                              base::string16* pnp_device_id,
+                              base::string16* storage_object_id) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   DCHECK(!storage_path.empty());
   DCHECK(pnp_device_id);
   DCHECK(storage_object_id);
-  string16 storage_device_id;
+  base::string16 storage_device_id;
   base::RemoveChars(storage_path, L"\\\\", &storage_device_id);
   DCHECK(!storage_device_id.empty());
   // TODO(gbillock): Take the StorageMonitor as an argument.
@@ -70,7 +70,7 @@ string16 GetFileObjectIdFromPathOnBlockingPoolThread(
       PortableDeviceMapService::GetInstance()->GetPortableDevice(
           device_info.registered_device_path);
   if (!device)
-    return string16();
+    return base::string16();
 
   if (device_info.registered_device_path == file_path.value())
     return device_info.storage_object_id;
@@ -78,13 +78,13 @@ string16 GetFileObjectIdFromPathOnBlockingPoolThread(
   base::FilePath relative_path;
   if (!base::FilePath(device_info.registered_device_path).AppendRelativePath(
           file_path, &relative_path))
-    return string16();
+    return base::string16();
 
   std::vector<string16> path_components;
   relative_path.GetComponents(&path_components);
   DCHECK(!path_components.empty());
-  string16 parent_id(device_info.storage_object_id);
-  string16 file_object_id;
+  base::string16 parent_id(device_info.storage_object_id);
+  base::string16 file_object_id;
   for (size_t i = 0; i < path_components.size(); ++i) {
     file_object_id =
         media_transfer_protocol::GetObjectIdFromName(device, parent_id,
@@ -111,8 +111,8 @@ CreateFileEnumeratorOnBlockingPoolThread(
   if (!device)
     return scoped_ptr<MTPDeviceObjectEnumerator>();
 
-  string16 object_id = GetFileObjectIdFromPathOnBlockingPoolThread(device_info,
-                                                                   root);
+  base::string16 object_id =
+      GetFileObjectIdFromPathOnBlockingPoolThread(device_info, root);
   if (object_id.empty())
     return scoped_ptr<MTPDeviceObjectEnumerator>();
 
@@ -130,8 +130,9 @@ CreateFileEnumeratorOnBlockingPoolThread(
 // |pnp_device_id| specifies the PnP device id.
 // |registered_device_path| specifies the registered file system root path for
 // the given device.
-bool OpenDeviceOnBlockingPoolThread(const string16& pnp_device_id,
-                                    const string16& registered_device_path) {
+bool OpenDeviceOnBlockingPoolThread(
+    const base::string16& pnp_device_id,
+    const base::string16& registered_device_path) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!pnp_device_id.empty());
   DCHECK(!registered_device_path.empty());
@@ -163,8 +164,8 @@ base::PlatformFileError GetFileInfoOnBlockingPoolThread(
   if (!device)
     return base::PLATFORM_FILE_ERROR_FAILED;
 
-  string16 object_id = GetFileObjectIdFromPathOnBlockingPoolThread(device_info,
-                                                                   file_path);
+  base::string16 object_id =
+      GetFileObjectIdFromPathOnBlockingPoolThread(device_info, file_path);
   if (object_id.empty())
     return base::PLATFORM_FILE_ERROR_FAILED;
   return media_transfer_protocol::GetFileEntryInfo(device, object_id,
@@ -227,7 +228,7 @@ base::PlatformFileError GetFileStreamOnBlockingPoolThread(
   if (!device)
     return base::PLATFORM_FILE_ERROR_FAILED;
 
-  string16 file_object_id =
+  base::string16 file_object_id =
       GetFileObjectIdFromPathOnBlockingPoolThread(
           device_info, file_details->request_info().device_file_path);
   if (file_object_id.empty())
@@ -286,7 +287,7 @@ DWORD WriteDataChunkIntoSnapshotFileOnBlockingPoolThread(
 }
 
 void DeletePortableDeviceOnBlockingPoolThread(
-    const string16& registered_device_path) {
+    const base::string16& registered_device_path) {
   base::ThreadRestrictions::AssertIOAllowed();
   PortableDeviceMapService::GetInstance()->RemovePortableDevice(
       registered_device_path);
@@ -297,10 +298,10 @@ void DeletePortableDeviceOnBlockingPoolThread(
 // Used by CreateMTPDeviceAsyncDelegate() to create the MTP device
 // delegate on the IO thread.
 void OnGetStorageInfoCreateDelegate(
-    const string16& device_location,
+    const base::string16& device_location,
     const CreateMTPDeviceAsyncDelegateCallback& callback,
-    string16* pnp_device_id,
-    string16* storage_object_id,
+    base::string16* pnp_device_id,
+    base::string16* storage_object_id,
     bool succeeded) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   DCHECK(pnp_device_id);
@@ -313,12 +314,12 @@ void OnGetStorageInfoCreateDelegate(
 }
 
 void CreateMTPDeviceAsyncDelegate(
-    const string16& device_location,
+    const base::string16& device_location,
     const CreateMTPDeviceAsyncDelegateCallback& callback) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   DCHECK(!device_location.empty());
-  string16* pnp_device_id = new string16;
-  string16* storage_object_id = new string16;
+  base::string16* pnp_device_id = new base::string16;
+  base::string16* storage_object_id = new base::string16;
   content::BrowserThread::PostTaskAndReplyWithResult<bool>(
       content::BrowserThread::UI,
       FROM_HERE,
@@ -336,9 +337,9 @@ void CreateMTPDeviceAsyncDelegate(
 // MTPDeviceDelegateImplWin ---------------------------------------------------
 
 MTPDeviceDelegateImplWin::StorageDeviceInfo::StorageDeviceInfo(
-    const string16& pnp_device_id,
-    const string16& registered_device_path,
-    const string16& storage_object_id)
+    const base::string16& pnp_device_id,
+    const base::string16& registered_device_path,
+    const base::string16& storage_object_id)
     : pnp_device_id(pnp_device_id),
       registered_device_path(registered_device_path),
       storage_object_id(storage_object_id) {
@@ -355,9 +356,9 @@ MTPDeviceDelegateImplWin::PendingTaskInfo::PendingTaskInfo(
 }
 
 MTPDeviceDelegateImplWin::MTPDeviceDelegateImplWin(
-    const string16& registered_device_path,
-    const string16& pnp_device_id,
-    const string16& storage_object_id)
+    const base::string16& registered_device_path,
+    const base::string16& pnp_device_id,
+    const base::string16& storage_object_id)
     : storage_device_info_(pnp_device_id, registered_device_path,
                            storage_object_id),
       init_state_(UNINITIALIZED),
diff --git a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.h b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.h
index 6d31894..8db1dfe 100644
--- a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.h
+++ b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win.h
@@ -37,30 +37,30 @@ class MTPDeviceDelegateImplWin : public MTPDeviceAsyncDelegate {
  public:
   // Structure used to represent MTP device storage partition details.
   struct StorageDeviceInfo {
-    StorageDeviceInfo(const string16& pnp_device_id,
-                      const string16& registered_device_path,
-                      const string16& storage_object_id);
+    StorageDeviceInfo(const base::string16& pnp_device_id,
+                      const base::string16& registered_device_path,
+                      const base::string16& storage_object_id);
 
     // The PnP Device Id, used to open the device for communication,
     // e.g. "\\?\usb#vid_04a9&pid_3073#12#{6ac27878-a6fa-4155-ba85-f1d4f33}".
-    const string16 pnp_device_id;
+    const base::string16 pnp_device_id;
 
     // The media file system root path, which is obtained during the
     // registration of MTP device storage partition as a file system,
     // e.g. "\\MTP:StorageSerial:SID-{10001,E,9823}:237483".
-    const string16 registered_device_path;
+    const base::string16 registered_device_path;
 
     // The MTP device storage partition object identifier, used to enumerate the
     // storage contents, e.g. "s10001".
-    const string16 storage_object_id;
+    const base::string16 storage_object_id;
   };
 
  private:
   friend void OnGetStorageInfoCreateDelegate(
-      const string16& device_location,
+      const base::string16& device_location,
       const CreateMTPDeviceAsyncDelegateCallback& callback,
-      string16* pnp_device_id,
-      string16* storage_object_id,
+      base::string16* pnp_device_id,
+      base::string16* storage_object_id,
       bool succeeded);
 
   enum InitializationState {
@@ -82,9 +82,9 @@ class MTPDeviceDelegateImplWin : public MTPDeviceAsyncDelegate {
 
   // Defers the device initializations until the first file operation request.
   // Do all the initializations in EnsureInitAndRunTask() function.
-  MTPDeviceDelegateImplWin(const string16& registered_device_path,
-                           const string16& pnp_device_id,
-                           const string16& storage_object_id);
+  MTPDeviceDelegateImplWin(const base::string16& registered_device_path,
+                           const base::string16& pnp_device_id,
+                           const base::string16& storage_object_id);
 
   // Destructed via CancelPendingTasksAndDeleteDelegate().
   virtual ~MTPDeviceDelegateImplWin();
diff --git a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win_unittest.cc b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win_unittest.cc
index 18c11b0..af4344b 100644
--- a/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win_unittest.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_delegate_impl_win_unittest.cc
@@ -49,13 +49,13 @@ class MTPDeviceDelegateImplWinTest : public ChromeRenderViewHostTestHarness {
   void TearDown() OVERRIDE;
 
   void ProcessAttach(const std::string& id,
-                     const string16& name,
+                     const base::string16& name,
                      const base::FilePath::StringType& location);
   std::string AttachDevice(StorageInfo::Type type,
                            const std::string& unique_id,
                            const base::FilePath& location);
   void CheckGalleryInfo(const MediaFileSystemInfo& info,
-                        const string16& name,
+                        const base::string16& name,
                         const base::FilePath& path,
                         bool removable,
                         bool media_device);
@@ -109,9 +109,10 @@ void MTPDeviceDelegateImplWinTest::TearDown() {
 
 void MTPDeviceDelegateImplWinTest::ProcessAttach(
     const std::string& id,
-    const string16& label,
+    const base::string16& label,
     const base::FilePath::StringType& location) {
-  StorageInfo info(id, string16(), location, label, string16(), string16(), 0);
+  StorageInfo info(id, base::string16(), location, label, base::string16(),
+                   base::string16(), 0);
   monitor_->receiver()->ProcessAttach(info);
 }
 
@@ -121,7 +122,7 @@ std::string MTPDeviceDelegateImplWinTest::AttachDevice(
     const base::FilePath& location) {
   std::string device_id = StorageInfo::MakeDeviceId(type, unique_id);
   DCHECK(StorageInfo::IsRemovableDevice(device_id));
-  string16 label = location.LossyDisplayName();
+  base::string16 label = location.LossyDisplayName();
   ProcessAttach(device_id, label, location.value());
   base::RunLoop().RunUntilIdle();
   return device_id;
@@ -129,7 +130,7 @@ std::string MTPDeviceDelegateImplWinTest::AttachDevice(
 
 void MTPDeviceDelegateImplWinTest::CheckGalleryInfo(
     const MediaFileSystemInfo& info,
-    const string16& name,
+    const base::string16& name,
     const base::FilePath& path,
     bool removable,
     bool media_device) {
diff --git a/chrome/browser/media_galleries/win/mtp_device_object_entry.cc b/chrome/browser/media_galleries/win/mtp_device_object_entry.cc
index 127ac01..4078fbb 100644
--- a/chrome/browser/media_galleries/win/mtp_device_object_entry.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_object_entry.cc
@@ -9,8 +9,8 @@
 MTPDeviceObjectEntry::MTPDeviceObjectEntry() : is_directory(false), size(0) {
 }
 
-MTPDeviceObjectEntry::MTPDeviceObjectEntry(const string16& object_id,
-                                           const string16& object_name,
+MTPDeviceObjectEntry::MTPDeviceObjectEntry(const base::string16& object_id,
+                                           const base::string16& object_name,
                                            bool is_directory,
                                            int64 size,
                                            const base::Time& last_modified_time)
diff --git a/chrome/browser/media_galleries/win/mtp_device_object_entry.h b/chrome/browser/media_galleries/win/mtp_device_object_entry.h
index 775e43b..b26652e 100644
--- a/chrome/browser/media_galleries/win/mtp_device_object_entry.h
+++ b/chrome/browser/media_galleries/win/mtp_device_object_entry.h
@@ -16,18 +16,18 @@
 // IPortableDeviceProperties::GetValues().
 struct MTPDeviceObjectEntry {
   MTPDeviceObjectEntry();  // Necessary for STL.
-  MTPDeviceObjectEntry(const string16& object_id,
-                       const string16& object_name,
+  MTPDeviceObjectEntry(const base::string16& object_id,
+                       const base::string16& object_name,
                        bool is_directory,
                        int64 size,
                        const base::Time& last_modified_time);
 
   // The object identifier obtained using IEnumPortableDeviceObjectIDs::Next(),
   // e.g. "o299".
-  string16 object_id;
+  base::string16 object_id;
 
   // Friendly name of the object, e.g. "IMG_9911.jpeg".
-  string16 name;
+  base::string16 name;
 
   // True if the current object is a directory/folder/album content type.
   bool is_directory;
diff --git a/chrome/browser/media_galleries/win/mtp_device_object_enumerator.cc b/chrome/browser/media_galleries/win/mtp_device_object_enumerator.cc
index 5414d0e..8c2fa8b 100644
--- a/chrome/browser/media_galleries/win/mtp_device_object_enumerator.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_object_enumerator.cc
@@ -57,7 +57,7 @@ base::Time MTPDeviceObjectEnumerator::LastModifiedTime() {
 string16 MTPDeviceObjectEnumerator::GetObjectId() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!IsIndexReadyAndInRange())
-    return string16();
+    return base::string16();
   return object_entries_[index_].object_id;
 }
 
diff --git a/chrome/browser/media_galleries/win/mtp_device_object_enumerator.h b/chrome/browser/media_galleries/win/mtp_device_object_enumerator.h
index ce2c3e9..a460f61 100644
--- a/chrome/browser/media_galleries/win/mtp_device_object_enumerator.h
+++ b/chrome/browser/media_galleries/win/mtp_device_object_enumerator.h
@@ -29,7 +29,7 @@ class MTPDeviceObjectEnumerator {
 
   // If the current file object entry is valid, returns an non-empty object id.
   // Returns an empty string otherwise.
-  string16 GetObjectId() const;
+  base::string16 GetObjectId() const;
 
  private:
   // Returns true if the enumerator has more entries to traverse, false
diff --git a/chrome/browser/media_galleries/win/mtp_device_object_enumerator_unittest.cc b/chrome/browser/media_galleries/win/mtp_device_object_enumerator_unittest.cc
index 7c2725c..85ddf08 100644
--- a/chrome/browser/media_galleries/win/mtp_device_object_enumerator_unittest.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_object_enumerator_unittest.cc
@@ -18,10 +18,10 @@ namespace {
 
 struct MTPDeviceObjectEntryData {
   // Friendly name of the object, e.g. "IMG_9911.jpeg".
-  string16 name;
+  base::string16 name;
 
   // The object identifier, e.g. "o299".
-  string16 object_id;
+  base::string16 object_id;
 
   // True if the current object is a directory/folder/album content type.
   bool is_directory;
diff --git a/chrome/browser/media_galleries/win/mtp_device_operations_util.cc b/chrome/browser/media_galleries/win/mtp_device_operations_util.cc
index 0d9ac6c1..8424183 100644
--- a/chrome/browser/media_galleries/win/mtp_device_operations_util.cc
+++ b/chrome/browser/media_galleries/win/mtp_device_operations_util.cc
@@ -69,7 +69,7 @@ base::win::ScopedComPtr<IPortableDeviceContent> GetDeviceContent(
 // |parent_id| specifies the parent object identifier.
 base::win::ScopedComPtr<IEnumPortableDeviceObjectIDs> GetDeviceObjectEnumerator(
     IPortableDevice* device,
-    const string16& parent_id) {
+    const base::string16& parent_id) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(device);
   DCHECK(!parent_id.empty());
@@ -106,14 +106,14 @@ bool IsDirectory(IPortableDeviceValues* properties_values) {
 
 // Returns the friendly name of the object from the property key values
 // specified by the |properties_values|.
-string16 GetObjectName(IPortableDeviceValues* properties_values,
+base::string16 GetObjectName(IPortableDeviceValues* properties_values,
                        bool is_directory) {
   DCHECK(properties_values);
   base::win::ScopedCoMem<char16> buffer;
   REFPROPERTYKEY key =
       is_directory ? WPD_OBJECT_NAME : WPD_OBJECT_ORIGINAL_FILE_NAME;
   HRESULT hr = properties_values->GetStringValue(key, &buffer);
-  string16 result;
+  base::string16 result;
   if (SUCCEEDED(hr))
     result.assign(buffer);
   return result;
@@ -165,8 +165,8 @@ bool GetObjectSize(IPortableDeviceValues* properties_values, int64* size) {
 // transfer protocol |device|. On success, returns true and fills in |name|,
 // |is_directory|, |size| and |last_modified_time|.
 bool GetObjectDetails(IPortableDevice* device,
-                      const string16 object_id,
-                      string16* name,
+                      const base::string16 object_id,
+                      base::string16* name,
                       bool* is_directory,
                       int64* size,
                       base::Time* last_modified_time) {
@@ -228,13 +228,13 @@ bool GetObjectDetails(IPortableDevice* device,
 // Creates an MTP device object entry for the given |device| and |object_id|.
 // On success, returns true and fills in |entry|.
 bool GetMTPDeviceObjectEntry(IPortableDevice* device,
-                             const string16& object_id,
+                             const base::string16& object_id,
                              MTPDeviceObjectEntry* entry) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(device);
   DCHECK(!object_id.empty());
   DCHECK(entry);
-  string16 name;
+  base::string16 name;
   bool is_directory;
   int64 size;
   base::Time last_modified_time;
@@ -252,8 +252,8 @@ bool GetMTPDeviceObjectEntry(IPortableDevice* device,
 // |object_name|. Leave |object_name| blank to request all entries. On
 // success returns true and set |object_entries|.
 bool GetMTPDeviceObjectEntries(IPortableDevice* device,
-                               const string16& directory_object_id,
-                               const string16& object_name,
+                               const base::string16& directory_object_id,
+                               const base::string16& object_name,
                                MTPDeviceObjectEntries* object_entries) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(device);
@@ -295,7 +295,7 @@ bool GetMTPDeviceObjectEntries(IPortableDevice* device,
 }  // namespace
 
 base::win::ScopedComPtr<IPortableDevice> OpenDevice(
-    const string16& pnp_device_id) {
+    const base::string16& pnp_device_id) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!pnp_device_id.empty());
   base::win::ScopedComPtr<IPortableDeviceValues> client_info;
@@ -317,7 +317,7 @@ base::win::ScopedComPtr<IPortableDevice> OpenDevice(
 
 base::PlatformFileError GetFileEntryInfo(
     IPortableDevice* device,
-    const string16& object_id,
+    const base::string16& object_id,
     base::PlatformFileInfo* file_entry_info) {
   DCHECK(device);
   DCHECK(!object_id.empty());
@@ -336,14 +336,14 @@ base::PlatformFileError GetFileEntryInfo(
 }
 
 bool GetDirectoryEntries(IPortableDevice* device,
-                         const string16& directory_object_id,
+                         const base::string16& directory_object_id,
                          MTPDeviceObjectEntries* object_entries) {
-  return GetMTPDeviceObjectEntries(device, directory_object_id, string16(),
-                                   object_entries);
+  return GetMTPDeviceObjectEntries(device, directory_object_id,
+                                   base::string16(), object_entries);
 }
 
 HRESULT GetFileStreamForObject(IPortableDevice* device,
-                               const string16& file_object_id,
+                               const base::string16& file_object_id,
                                IStream** file_stream,
                                DWORD* optimal_transfer_size) {
   base::ThreadRestrictions::AssertIOAllowed();
@@ -392,14 +392,14 @@ DWORD CopyDataChunkToLocalFile(IStream* stream,
   return data_len;
 }
 
-string16 GetObjectIdFromName(IPortableDevice* device,
-                             const string16& parent_id,
-                             const string16& object_name) {
+base::string16 GetObjectIdFromName(IPortableDevice* device,
+                                   const base::string16& parent_id,
+                                   const base::string16& object_name) {
   MTPDeviceObjectEntries object_entries;
   if (!GetMTPDeviceObjectEntries(device, parent_id, object_name,
                                  &object_entries) ||
       object_entries.empty())
-    return string16();
+    return base::string16();
   // TODO(thestig): This DCHECK can fail. Multiple MTP objects can have
   // the same name. Handle the situation gracefully. Refer to crbug.com/169930
   // for more details.
diff --git a/chrome/browser/media_galleries/win/mtp_device_operations_util.h b/chrome/browser/media_galleries/win/mtp_device_operations_util.h
index d11de86..7fb7229 100644
--- a/chrome/browser/media_galleries/win/mtp_device_operations_util.h
+++ b/chrome/browser/media_galleries/win/mtp_device_operations_util.h
@@ -26,7 +26,7 @@ namespace media_transfer_protocol {
 // play device ID string. On success, returns the IPortableDevice interface.
 // On failure, returns NULL.
 base::win::ScopedComPtr<IPortableDevice> OpenDevice(
-    const string16& pnp_device_id);
+    const base::string16& pnp_device_id);
 
 // Gets the details of the object specified by |object_id| from the given MTP
 // |device|. On success, returns no error (base::PLATFORM_FILE_OK) and fills in
@@ -34,7 +34,7 @@ base::win::ScopedComPtr<IPortableDevice> OpenDevice(
 // and |file_entry_info| is not set.
 base::PlatformFileError GetFileEntryInfo(
     IPortableDevice* device,
-    const string16& object_id,
+    const base::string16& object_id,
     base::PlatformFileInfo* file_entry_info);
 
 // Gets the entries of the directory specified by |directory_object_id| from
@@ -42,7 +42,7 @@ base::PlatformFileError GetFileEntryInfo(
 // |object_entries|. On failure, returns false and |object_entries| is not
 // set.
 bool GetDirectoryEntries(IPortableDevice* device,
-                         const string16& directory_object_id,
+                         const base::string16& directory_object_id,
                          MTPDeviceObjectEntries* object_entries);
 
 // Gets an IStream interface to read the object content data from the |device|.
@@ -51,7 +51,7 @@ bool GetDirectoryEntries(IPortableDevice* device,
 // On failure, returns an error code and |file_stream| and
 // |optimal_transfer_size| are not set.
 HRESULT GetFileStreamForObject(IPortableDevice* device,
-                               const string16& file_object_id,
+                               const base::string16& file_object_id,
                                IStream** file_stream,
                                DWORD* optimal_transfer_size);
 
@@ -74,8 +74,8 @@ DWORD CopyDataChunkToLocalFile(IStream* stream,
 // |parent_id| specifies the object's parent identifier.
 // |object_name| specifies the friendly name of the object.
 string16 GetObjectIdFromName(IPortableDevice* device,
-                             const string16& parent_id,
-                             const string16& object_name);
+                             const base::string16& parent_id,
+                             const base::string16& object_name);
 
 }  // namespace media_transfer_protocol
 
diff --git a/chrome/browser/media_galleries/win/portable_device_map_service.cc b/chrome/browser/media_galleries/win/portable_device_map_service.cc
index 557353e..82b8eb4 100644
--- a/chrome/browser/media_galleries/win/portable_device_map_service.cc
+++ b/chrome/browser/media_galleries/win/portable_device_map_service.cc
@@ -22,7 +22,7 @@ PortableDeviceMapService* PortableDeviceMapService::GetInstance() {
 }
 
 void PortableDeviceMapService::AddPortableDevice(
-    const string16& device_location,
+    const base::string16& device_location,
     IPortableDevice* device) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!device_location.empty());
@@ -32,7 +32,7 @@ void PortableDeviceMapService::AddPortableDevice(
 }
 
 void PortableDeviceMapService::MarkPortableDeviceForDeletion(
-    const string16& device_location) {
+    const base::string16& device_location) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   DCHECK(!device_location.empty());
   base::AutoLock lock(lock_);
@@ -42,7 +42,7 @@ void PortableDeviceMapService::MarkPortableDeviceForDeletion(
 }
 
 void PortableDeviceMapService::RemovePortableDevice(
-    const string16& device_location) {
+    const base::string16& device_location) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!device_location.empty());
   base::AutoLock lock(lock_);
@@ -52,7 +52,7 @@ void PortableDeviceMapService::RemovePortableDevice(
 }
 
 IPortableDevice* PortableDeviceMapService::GetPortableDevice(
-    const string16& device_location) {
+    const base::string16& device_location) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!device_location.empty());
   base::AutoLock lock(lock_);
diff --git a/chrome/browser/media_galleries/win/portable_device_map_service.h b/chrome/browser/media_galleries/win/portable_device_map_service.h
index 01a5900..16e4567 100644
--- a/chrome/browser/media_galleries/win/portable_device_map_service.h
+++ b/chrome/browser/media_galleries/win/portable_device_map_service.h
@@ -21,7 +21,7 @@ class PortableDeviceMapService {
 
   // Adds the portable |device| interface to the map service for the device
   // specified by the |device_location|. Called on a blocking pool thread.
-  void AddPortableDevice(const string16& device_location,
+  void AddPortableDevice(const base::string16& device_location,
                          IPortableDevice* device);
 
   // Marks the IPortableDevice interface of the device specified by the
@@ -32,19 +32,19 @@ class PortableDeviceMapService {
   // remove the IPortableDevice interface from the map service.
   //
   // Called on the IO thread.
-  void MarkPortableDeviceForDeletion(const string16& device_location);
+  void MarkPortableDeviceForDeletion(const base::string16& device_location);
 
   // Removes the IPortableDevice interface from the map service for the device
   // specified by the |device_location|. Callers of this function should have
   // already called MarkPortableDeviceForDeletion() on the IO thread.
   // Called on a blocking pool thread.
-  void RemovePortableDevice(const string16& device_location);
+  void RemovePortableDevice(const base::string16& device_location);
 
   // Gets the IPortableDevice interface associated with the device specified
   // by the |device_location|. Returns NULL if the |device_location| is no
   // longer valid (e.g. the corresponding device is detached etc).
   // Called on a blocking pool thread.
-  IPortableDevice* GetPortableDevice(const string16& device_location);
+  IPortableDevice* GetPortableDevice(const base::string16& device_location);
 
  private:
   friend struct base::DefaultLazyInstanceTraits<PortableDeviceMapService>;
@@ -60,7 +60,7 @@ class PortableDeviceMapService {
     bool scheduled_to_delete;
   };
 
-  typedef std::map<const string16, PortableDeviceInfo> PortableDeviceMap;
+  typedef std::map<const base::string16, PortableDeviceInfo> PortableDeviceMap;
 
   // Get access to this class using GetInstance() method.
   PortableDeviceMapService();
diff --git a/chrome/browser/memory_details.h b/chrome/browser/memory_details.h
index fb2ebb3..8756acd 100644
--- a/chrome/browser/memory_details.h
+++ b/chrome/browser/memory_details.h
@@ -48,9 +48,9 @@ struct ProcessMemoryInformation {
   // The committed bytes.
   base::CommittedKBytes committed;
   // The process version
-  string16 version;
+  base::string16 version;
   // The process product name.
-  string16 product_name;
+  base::string16 product_name;
   // The number of processes which this memory represents.
   int num_processes;
   // A process is a diagnostics process if it is rendering about:memory.
@@ -74,8 +74,8 @@ struct ProcessData {
   ~ProcessData();
   ProcessData& operator=(const ProcessData& rhs);
 
-  string16 name;
-  string16 process_name;
+  base::string16 name;
+  base::string16 process_name;
   ProcessMemoryInformationList processes;
 
   // Track site data for predicting process counts with out-of-process iframes.
diff --git a/chrome/browser/metrics/metrics_log.cc b/chrome/browser/metrics/metrics_log.cc
index f286d1f..72d738b 100644
--- a/chrome/browser/metrics/metrics_log.cc
+++ b/chrome/browser/metrics/metrics_log.cc
@@ -874,7 +874,7 @@ void MetricsLog::RecordOmniboxOpenedURL(const OmniboxLog& log) {
   omnibox_event->set_just_deleted_text(log.just_deleted_text);
   omnibox_event->set_num_typed_terms(num_terms);
   omnibox_event->set_selected_index(log.selected_index);
-  if (log.completed_length != string16::npos)
+  if (log.completed_length != base::string16::npos)
     omnibox_event->set_completed_length(log.completed_length);
   if (log.elapsed_time_since_user_first_modified_omnibox !=
       base::TimeDelta::FromMilliseconds(-1)) {
diff --git a/chrome/browser/metrics/metrics_service.cc b/chrome/browser/metrics/metrics_service.cc
index d3993e1..bffc614 100644
--- a/chrome/browser/metrics/metrics_service.cc
+++ b/chrome/browser/metrics/metrics_service.cc
@@ -1792,7 +1792,7 @@ void MetricsService::LogPluginLoadingError(const base::FilePath& plugin_path) {
 
 MetricsService::ChildProcessStats& MetricsService::GetChildProcessStats(
     const content::ChildProcessData& data) {
-  const string16& child_name = data.name;
+  const base::string16& child_name = data.name;
   if (!ContainsKey(child_process_stats_buffer_, child_name)) {
     child_process_stats_buffer_[child_name] =
         ChildProcessStats(data.process_type);
@@ -1821,7 +1821,7 @@ void MetricsService::RecordPluginChanges(PrefService* pref) {
     }
 
     // TODO(viettrungluu): remove conversions
-    string16 name16 = UTF8ToUTF16(plugin_name);
+    base::string16 name16 = UTF8ToUTF16(plugin_name);
     if (child_process_stats_buffer_.find(name16) ==
         child_process_stats_buffer_.end()) {
       continue;
diff --git a/chrome/browser/metrics/variations/variations_registry_syncer_win.cc b/chrome/browser/metrics/variations/variations_registry_syncer_win.cc
index 3f24e41..6f092e6 100644
--- a/chrome/browser/metrics/variations/variations_registry_syncer_win.cc
+++ b/chrome/browser/metrics/variations/variations_registry_syncer_win.cc
@@ -50,7 +50,7 @@ void VariationsRegistrySyncer::SyncWithRegistry() {
       !InstallUtil::IsPerUserInstall(chrome_exe.value().c_str());
 
   // Read the current bits from the registry.
-  string16 registry_labels;
+  base::string16 registry_labels;
   bool success = GoogleUpdateSettings::ReadExperimentLabels(is_system_install,
                                                             &registry_labels);
   if (!success) {
@@ -60,17 +60,18 @@ void VariationsRegistrySyncer::SyncWithRegistry() {
 
   // Since the non-Variations contents of experiment_labels should not be,
   // clobbered, separate them from the Variations contents.
-  const string16 other_labels = ExtractNonVariationLabels(registry_labels);
+  const base::string16 other_labels =
+      ExtractNonVariationLabels(registry_labels);
 
   // Compute the new Variations part of the label.
   base::FieldTrial::ActiveGroups active_groups;
   base::FieldTrialList::GetActiveFieldTrialGroups(&active_groups);
-  const string16 variation_labels =
+  const base::string16 variation_labels =
       BuildGoogleUpdateExperimentLabel(active_groups);
 
   // Append the old non-Variations labels with the new Variations labels and
   // write it back to the registry.
-  const string16 combined_labels =
+  const base::string16 combined_labels =
       CombineExperimentLabels(variation_labels, other_labels);
 
   if (!GoogleUpdateSettings::SetExperimentLabels(is_system_install,
diff --git a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
index d5fc136..bd72501 100644
--- a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
+++ b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc
@@ -133,12 +133,12 @@ void ChromeMetroViewerProcessHost::OnSetTargetSurface(
       content::NotificationService::NoDetails());
 }
 
-void ChromeMetroViewerProcessHost::OnOpenURL(const string16& url) {
+void ChromeMetroViewerProcessHost::OnOpenURL(const base::string16& url) {
   OpenURL(GURL(url));
 }
 
 void ChromeMetroViewerProcessHost::OnHandleSearchRequest(
-    const string16& search_string) {
+    const base::string16& search_string) {
   GURL url(GetDefaultSearchURLForSearchTerms(
       ProfileManager::GetDefaultProfileOrOffTheRecord(), search_string));
   if (url.is_valid())
diff --git a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.h b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.h
index c32e597..69c10c3 100644
--- a/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.h
+++ b/chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.h
@@ -17,8 +17,9 @@ class ChromeMetroViewerProcessHost : public win8::MetroViewerProcessHost {
   // IPC::Listener implementation
   virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;
   virtual void OnSetTargetSurface(gfx::NativeViewId target_surface) OVERRIDE;
-  virtual void OnOpenURL(const string16& url) OVERRIDE;
-  virtual void OnHandleSearchRequest(const string16& search_string) OVERRIDE;
+  virtual void OnOpenURL(const base::string16& url) OVERRIDE;
+  virtual void OnHandleSearchRequest(
+      const base::string16& search_string) OVERRIDE;
   virtual void OnWindowSizeChanged(uint32 width, uint32 height) OVERRIDE;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeMetroViewerProcessHost);
diff --git a/chrome/browser/net/chrome_network_delegate.cc b/chrome/browser/net/chrome_network_delegate.cc
index 9deb2f8..e021791 100644
--- a/chrome/browser/net/chrome_network_delegate.cc
+++ b/chrome/browser/net/chrome_network_delegate.cc
@@ -576,7 +576,7 @@ void ChromeNetworkDelegate::OnURLRequestDestroyed(net::URLRequest* request) {
 }
 
 void ChromeNetworkDelegate::OnPACScriptError(int line_number,
-                                             const string16& error) {
+                                             const base::string16& error) {
   extensions::ProxyEventRouter::GetInstance()->OnPACScriptError(
       event_router_.get(), profile_, line_number, error);
 }
diff --git a/chrome/browser/net/chrome_network_delegate.h b/chrome/browser/net/chrome_network_delegate.h
index 2aa2c45..84f5d09 100644
--- a/chrome/browser/net/chrome_network_delegate.h
+++ b/chrome/browser/net/chrome_network_delegate.h
@@ -155,7 +155,7 @@ class ChromeNetworkDelegate : public net::NetworkDelegate {
   virtual void OnCompleted(net::URLRequest* request, bool started) OVERRIDE;
   virtual void OnURLRequestDestroyed(net::URLRequest* request) OVERRIDE;
   virtual void OnPACScriptError(int line_number,
-                                const string16& error) OVERRIDE;
+                                const base::string16& error) OVERRIDE;
   virtual net::NetworkDelegate::AuthRequiredResponse OnAuthRequired(
       net::URLRequest* request,
       const net::AuthChallengeInfo& auth_info,
diff --git a/chrome/browser/net/connection_tester.cc b/chrome/browser/net/connection_tester.cc
index 0d38a6c..c9d1dad 100644
--- a/chrome/browser/net/connection_tester.cc
+++ b/chrome/browser/net/connection_tester.cc
@@ -473,7 +473,7 @@ string16 ConnectionTester::ProxySettingsExperimentDescription(
       return ASCIIToUTF16("Auto-detect proxy settings");
     default:
       NOTREACHED();
-      return string16();
+      return base::string16();
   }
 }
 
@@ -483,14 +483,14 @@ string16 ConnectionTester::HostResolverExperimentDescription(
   // TODO(eroman): Use proper string resources.
   switch (experiment) {
     case HOST_RESOLVER_EXPERIMENT_PLAIN:
-      return string16();
+      return base::string16();
     case HOST_RESOLVER_EXPERIMENT_DISABLE_IPV6:
       return ASCIIToUTF16("Disable IPv6 host resolving");
     case HOST_RESOLVER_EXPERIMENT_IPV6_PROBE:
       return ASCIIToUTF16("Probe for IPv6 host resolving");
     default:
       NOTREACHED();
-      return string16();
+      return base::string16();
   }
 }
 
diff --git a/chrome/browser/net/connection_tester.h b/chrome/browser/net/connection_tester.h
index df1bf34..ba9dec9 100644
--- a/chrome/browser/net/connection_tester.h
+++ b/chrome/browser/net/connection_tester.h
@@ -140,9 +140,9 @@ class ConnectionTester {
   void RunAllTests(const GURL& url);
 
   // Returns a text string explaining what |experiment| is testing.
-  static string16 ProxySettingsExperimentDescription(
+  static base::string16 ProxySettingsExperimentDescription(
       ProxySettingsExperiment experiment);
-  static string16 HostResolverExperimentDescription(
+  static base::string16 HostResolverExperimentDescription(
       HostResolverExperiment experiment);
 
  private:
diff --git a/chrome/browser/net/net_error_tab_helper.cc b/chrome/browser/net/net_error_tab_helper.cc
index 4243ed2..a00ad62 100644
--- a/chrome/browser/net/net_error_tab_helper.cc
+++ b/chrome/browser/net/net_error_tab_helper.cc
@@ -93,7 +93,7 @@ void NetErrorTabHelper::DidStartProvisionalLoadForFrame(
 
 void NetErrorTabHelper::DidCommitProvisionalLoadForFrame(
     int64 frame_id,
-    const string16& frame_unique_name,
+    const base::string16& frame_unique_name,
     bool is_main_frame,
     const GURL& url,
     PageTransition transition_type,
@@ -119,11 +119,11 @@ void NetErrorTabHelper::DidCommitProvisionalLoadForFrame(
 
 void NetErrorTabHelper::DidFailProvisionalLoad(
     int64 frame_id,
-    const string16& frame_unique_name,
+    const base::string16& frame_unique_name,
     bool is_main_frame,
     const GURL& validated_url,
     int error_code,
-    const string16& error_description,
+    const base::string16& error_description,
     RenderViewHost* render_view_host) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
diff --git a/chrome/browser/net/net_error_tab_helper.h b/chrome/browser/net/net_error_tab_helper.h
index c091f8b..90b0133 100644
--- a/chrome/browser/net/net_error_tab_helper.h
+++ b/chrome/browser/net/net_error_tab_helper.h
@@ -57,7 +57,7 @@ class NetErrorTabHelper
 
   virtual void DidCommitProvisionalLoadForFrame(
       int64 frame_id,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& url,
       content::PageTransition transition_type,
@@ -65,11 +65,11 @@ class NetErrorTabHelper
 
   virtual void DidFailProvisionalLoad(
       int64 frame_id,
-      const string16& frame_unique_name,
+      const base::string16& frame_unique_name,
       bool is_main_frame,
       const GURL& validated_url,
       int error_code,
-      const string16& error_description,
+      const base::string16& error_description,
       content::RenderViewHost* render_view_host) OVERRIDE;
 
  protected:
diff --git a/chrome/browser/net/net_error_tab_helper_unittest.cc b/chrome/browser/net/net_error_tab_helper_unittest.cc
index 488faeb..b643290 100644
--- a/chrome/browser/net/net_error_tab_helper_unittest.cc
+++ b/chrome/browser/net/net_error_tab_helper_unittest.cc
@@ -78,7 +78,7 @@ class NetErrorTabHelperTest : public testing::Test {
   void CommitProvisionalLoad(MainFrame main_frame) {
     tab_helper_.DidCommitProvisionalLoadForFrame(
         1,  // frame id
-        string16(),
+        base::string16(),
         (main_frame == MAIN_FRAME),
         bogus_url_,  // url
         content::PAGE_TRANSITION_TYPED,
@@ -95,11 +95,11 @@ class NetErrorTabHelperTest : public testing::Test {
 
     tab_helper_.DidFailProvisionalLoad(
         1,  // frame id
-        string16(),
+        base::string16(),
         (main_frame == MAIN_FRAME),
         bogus_url_,  // validated_url
         net_error,
-        string16(),
+        base::string16(),
         NULL);  // render_view_host
   }
 
diff --git a/chrome/browser/net/proxy_browsertest.cc b/chrome/browser/net/proxy_browsertest.cc
index 5897396..8b92d2b 100644
--- a/chrome/browser/net/proxy_browsertest.cc
+++ b/chrome/browser/net/proxy_browsertest.cc
@@ -137,7 +137,7 @@ IN_PROC_BROWSER_TEST_F(ProxyBrowserTest, MAYBE_BasicAuthWSConnect) {
       browser(),
       ws_server.GetURL("connect_check.html").ReplaceComponents(replacements));
 
-  const string16 result = watcher.WaitAndGetTitle();
+  const base::string16 result = watcher.WaitAndGetTitle();
   EXPECT_TRUE(EqualsASCII(result, "PASS"));
   EXPECT_TRUE(observer.auth_handled());
 }
diff --git a/chrome/browser/net/websocket_browsertest.cc b/chrome/browser/net/websocket_browsertest.cc
index 444a032..58b4f65 100644
--- a/chrome/browser/net/websocket_browsertest.cc
+++ b/chrome/browser/net/websocket_browsertest.cc
@@ -56,7 +56,7 @@ IN_PROC_BROWSER_TEST_F(WebSocketBrowserTest, WebSocketSplitSegments) {
       ws_server_.GetURL(
           "split_packet_check.html").ReplaceComponents(replacements));
 
-  const string16 result = watcher.WaitAndGetTitle();
+  const base::string16 result = watcher.WaitAndGetTitle();
   EXPECT_TRUE(EqualsASCII(result, "PASS"));
 }
 
@@ -87,7 +87,7 @@ IN_PROC_BROWSER_TEST_F(WebSocketBrowserTest,
       wss_server_.GetURL(
           "split_packet_check.html").ReplaceComponents(replacements));
 
-  const string16 result = watcher.WaitAndGetTitle();
+  const base::string16 result = watcher.WaitAndGetTitle();
   EXPECT_TRUE(EqualsASCII(result, "PASS"));
 }
 
diff --git a/chrome/browser/notifications/balloon_host.cc b/chrome/browser/notifications/balloon_host.cc
index c3de873..89a73e4 100644
--- a/chrome/browser/notifications/balloon_host.cc
+++ b/chrome/browser/notifications/balloon_host.cc
@@ -61,7 +61,7 @@ content::WebContents* BalloonHost::GetAssociatedWebContents() const {
   return NULL;
 }
 
-const string16& BalloonHost::GetSource() const {
+const base::string16& BalloonHost::GetSource() const {
   return balloon_->notification().display_source();
 }
 
diff --git a/chrome/browser/notifications/balloon_host.h b/chrome/browser/notifications/balloon_host.h
index 693b21b..c87f43e 100644
--- a/chrome/browser/notifications/balloon_host.h
+++ b/chrome/browser/notifications/balloon_host.h
@@ -39,7 +39,7 @@ class BalloonHost : public content::WebContentsDelegate,
       const OVERRIDE;
   virtual content::WebContents* GetAssociatedWebContents() const OVERRIDE;
 
-  const string16& GetSource() const;
+  const base::string16& GetSource() const;
 
   content::WebContents* web_contents() const { return web_contents_.get(); }
 
diff --git a/chrome/browser/notifications/balloon_notification_ui_manager.cc b/chrome/browser/notifications/balloon_notification_ui_manager.cc
index 6a946f5..a420ce5 100644
--- a/chrome/browser/notifications/balloon_notification_ui_manager.cc
+++ b/chrome/browser/notifications/balloon_notification_ui_manager.cc
@@ -90,7 +90,7 @@ void BalloonNotificationUIManager::Add(const Notification& notification,
 bool BalloonNotificationUIManager::Update(const Notification& notification,
                                           Profile* profile) {
   const GURL& origin = notification.origin_url();
-  const string16& replace_id = notification.replace_id();
+  const base::string16& replace_id = notification.replace_id();
 
   if (replace_id.empty())
     return false;
@@ -226,7 +226,7 @@ bool BalloonNotificationUIManager::UpdateNotification(
     const Notification& notification,
     Profile* profile) {
   const GURL& origin = notification.origin_url();
-  const string16& replace_id = notification.replace_id();
+  const base::string16& replace_id = notification.replace_id();
 
   DCHECK(!replace_id.empty());
 
diff --git a/chrome/browser/notifications/desktop_notification_service.cc b/chrome/browser/notifications/desktop_notification_service.cc
index 5a16feb..eecc9be 100644
--- a/chrome/browser/notifications/desktop_notification_service.cc
+++ b/chrome/browser/notifications/desktop_notification_service.cc
@@ -69,7 +69,7 @@ class NotificationPermissionInfoBarDelegate : public ConfirmInfoBarDelegate {
   static void Create(InfoBarService* infobar_service,
                      DesktopNotificationService* notification_service,
                      const GURL& origin,
-                     const string16& display_name,
+                     const base::string16& display_name,
                      int process_id,
                      int route_id,
                      int callback_context);
@@ -78,7 +78,7 @@ class NotificationPermissionInfoBarDelegate : public ConfirmInfoBarDelegate {
   NotificationPermissionInfoBarDelegate(
       DesktopNotificationService* notification_service,
       const GURL& origin,
-      const string16& display_name,
+      const base::string16& display_name,
       int process_id,
       int route_id,
       int callback_context);
@@ -87,8 +87,8 @@ class NotificationPermissionInfoBarDelegate : public ConfirmInfoBarDelegate {
   // ConfirmInfoBarDelegate:
   virtual int GetIconID() const OVERRIDE;
   virtual Type GetInfoBarType() const OVERRIDE;
-  virtual string16 GetMessageText() const OVERRIDE;
-  virtual string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
+  virtual base::string16 GetMessageText() const OVERRIDE;
+  virtual base::string16 GetButtonLabel(InfoBarButton button) const OVERRIDE;
   virtual bool Accept() OVERRIDE;
   virtual bool Cancel() OVERRIDE;
 
@@ -97,7 +97,7 @@ class NotificationPermissionInfoBarDelegate : public ConfirmInfoBarDelegate {
 
   // The display name for the origin to be displayed.  Will be different from
   // origin_ for extensions.
-  string16 display_name_;
+  base::string16 display_name_;
 
   // The notification service to be used.
   DesktopNotificationService* notification_service_;
@@ -119,7 +119,7 @@ void NotificationPermissionInfoBarDelegate::Create(
     InfoBarService* infobar_service,
     DesktopNotificationService* notification_service,
     const GURL& origin,
-    const string16& display_name,
+    const base::string16& display_name,
     int process_id,
     int route_id,
     int callback_context) {
@@ -133,7 +133,7 @@ void NotificationPermissionInfoBarDelegate::Create(
 NotificationPermissionInfoBarDelegate::NotificationPermissionInfoBarDelegate(
     DesktopNotificationService* notification_service,
     const GURL& origin,
-    const string16& display_name,
+    const base::string16& display_name,
     int process_id,
     int route_id,
     int callback_context)
@@ -166,12 +166,12 @@ InfoBarDelegate::Type
   return PAGE_ACTION_TYPE;
 }
 
-string16 NotificationPermissionInfoBarDelegate::GetMessageText() const {
+base::string16 NotificationPermissionInfoBarDelegate::GetMessageText() const {
   return l10n_util::GetStringFUTF16(IDS_NOTIFICATION_PERMISSIONS,
                                     display_name_);
 }
 
-string16 NotificationPermissionInfoBarDelegate::GetButtonLabel(
+base::string16 NotificationPermissionInfoBarDelegate::GetButtonLabel(
     InfoBarButton button) const {
   return l10n_util::GetStringUTF16((button == BUTTON_OK) ?
       IDS_NOTIFICATION_PERMISSION_YES : IDS_NOTIFICATION_PERMISSION_NO);
@@ -210,8 +210,10 @@ void DesktopNotificationService::RegisterProfilePrefs(
 }
 
 // static
-string16 DesktopNotificationService::CreateDataUrl(
-    const GURL& icon_url, const string16& title, const string16& body,
+base::string16 DesktopNotificationService::CreateDataUrl(
+    const GURL& icon_url,
+    const base::string16& title,
+    const base::string16& body,
     WebTextDirection dir) {
   int resource;
   std::vector<std::string> subst;
@@ -225,9 +227,9 @@ string16 DesktopNotificationService::CreateDataUrl(
                     "right" : "left");
   } else if (title.empty() || body.empty()) {
     resource = IDR_NOTIFICATION_1LINE_HTML;
-    string16 line = title.empty() ? body : title;
+    base::string16 line = title.empty() ? body : title;
     // Strings are div names in the template file.
-    string16 line_name = title.empty() ? ASCIIToUTF16("description")
+    base::string16 line_name = title.empty() ? ASCIIToUTF16("description")
                                        : ASCIIToUTF16("title");
     subst.push_back(net::EscapeForHTML(UTF16ToUTF8(line_name)));
     subst.push_back(net::EscapeForHTML(UTF16ToUTF8(line)));
@@ -244,7 +246,7 @@ string16 DesktopNotificationService::CreateDataUrl(
 }
 
 // static
-string16 DesktopNotificationService::CreateDataUrl(
+base::string16 DesktopNotificationService::CreateDataUrl(
     int resource, const std::vector<std::string>& subst) {
   const base::StringPiece template_html(
       ResourceBundle::GetSharedInstance().GetRawDataResource(
@@ -252,7 +254,7 @@ string16 DesktopNotificationService::CreateDataUrl(
 
   if (template_html.empty()) {
     NOTREACHED() << "unable to load template. ID: " << resource;
-    return string16();
+    return base::string16();
   }
 
   std::string data = ReplaceStringPlaceholders(template_html, subst, NULL);
@@ -263,17 +265,17 @@ string16 DesktopNotificationService::CreateDataUrl(
 // static
 std::string DesktopNotificationService::AddNotification(
     const GURL& origin_url,
-    const string16& title,
-    const string16& message,
+    const base::string16& title,
+    const base::string16& message,
     const GURL& icon_url,
-    const string16& replace_id,
+    const base::string16& replace_id,
     NotificationDelegate* delegate,
     Profile* profile) {
   if (message_center::IsRichNotificationEnabled()) {
     // For message center create a non-HTML notification with |icon_url|.
     Notification notification(origin_url, icon_url, title, message,
                               blink::WebTextDirectionDefault,
-                              string16(), replace_id, delegate);
+                              base::string16(), replace_id, delegate);
     g_browser_process->notification_ui_manager()->Add(notification, profile);
     return notification.notification_id();
   }
@@ -282,7 +284,7 @@ std::string DesktopNotificationService::AddNotification(
   GURL content_url(CreateDataUrl(
       icon_url, title, message, blink::WebTextDirectionDefault));
   Notification notification(
-      GURL(), content_url, string16(), replace_id, delegate);
+      GURL(), content_url, base::string16(), replace_id, delegate);
   g_browser_process->notification_ui_manager()->Add(notification, profile);
   return notification.notification_id();
 }
@@ -290,17 +292,17 @@ std::string DesktopNotificationService::AddNotification(
 // static
 std::string DesktopNotificationService::AddIconNotification(
     const GURL& origin_url,
-    const string16& title,
-    const string16& message,
+    const base::string16& title,
+    const base::string16& message,
     const gfx::Image& icon,
-    const string16& replace_id,
+    const base::string16& replace_id,
     NotificationDelegate* delegate,
     Profile* profile) {
   if (message_center::IsRichNotificationEnabled()) {
     // For message center create a non-HTML notification with |icon|.
     Notification notification(origin_url, icon, title, message,
                               blink::WebTextDirectionDefault,
-                              string16(), replace_id, delegate);
+                              base::string16(), replace_id, delegate);
     g_browser_process->notification_ui_manager()->Add(notification, profile);
     return notification.notification_id();
   }
@@ -489,7 +491,8 @@ bool DesktopNotificationService::ShowDesktopNotification(
                                   params.notification_id,
                                   source == WorkerNotification);
 
-  string16 display_source = DisplayNameForOriginInProcessId(origin, process_id);
+  base::string16 display_source =
+      DisplayNameForOriginInProcessId(origin, process_id);
   Notification notification(origin, params.icon_url, params.title,
       params.body, params.direction, display_source, params.replace_id,
       proxy);
@@ -501,7 +504,7 @@ bool DesktopNotificationService::ShowDesktopNotification(
   return true;
 }
 
-string16 DesktopNotificationService::DisplayNameForOriginInProcessId(
+base::string16 DesktopNotificationService::DisplayNameForOriginInProcessId(
     const GURL& origin, int process_id) {
   // If the source is an extension, lookup the display name.
   // Message center prefers to use extension name if the notification
diff --git a/chrome/browser/notifications/desktop_notification_service.h b/chrome/browser/notifications/desktop_notification_service.h
index c4bf961..b08e539 100644
--- a/chrome/browser/notifications/desktop_notification_service.h
+++ b/chrome/browser/notifications/desktop_notification_service.h
@@ -94,15 +94,15 @@ class DesktopNotificationService : public BrowserContextKeyedService,
   // Creates a data:xxxx URL which contains the full HTML for a notification
   // using supplied icon, title, and text, run through a template which contains
   // the standard formatting for notifications.
-  static string16 CreateDataUrl(const GURL& icon_url,
-                                const string16& title,
-                                const string16& body,
-                                blink::WebTextDirection dir);
+  static base::string16 CreateDataUrl(const GURL& icon_url,
+                                      const base::string16& title,
+                                      const base::string16& body,
+                                      blink::WebTextDirection dir);
 
   // Creates a data:xxxx URL which contains the full HTML for a notification
   // using resource template which contains the standard formatting for
   // notifications.
-  static string16 CreateDataUrl(int resource,
+  static base::string16 CreateDataUrl(int resource,
                                 const std::vector<std::string>& subst);
 
   // Add a desktop notification. On non-Ash platforms this will generate a HTML
@@ -111,19 +111,19 @@ class DesktopNotificationService : public BrowserContextKeyedService,
   // TODO(mukai): remove these methods. HTML notifications are no longer
   // supported.
   static std::string AddNotification(const GURL& origin_url,
-                                     const string16& title,
-                                     const string16& message,
+                                     const base::string16& title,
+                                     const base::string16& message,
                                      const GURL& icon_url,
-                                     const string16& replace_id,
+                                     const base::string16& replace_id,
                                      NotificationDelegate* delegate,
                                      Profile* profile);
 
   // Same as above, but takes a gfx::Image for the icon instead.
   static std::string AddIconNotification(const GURL& origin_url,
-                                         const string16& title,
-                                         const string16& message,
+                                         const base::string16& title,
+                                         const base::string16& message,
                                          const gfx::Image& icon,
-                                         const string16& replace_id,
+                                         const base::string16& replace_id,
                                          NotificationDelegate* delegate,
                                          Profile* profile);
 
@@ -170,7 +170,8 @@ class DesktopNotificationService : public BrowserContextKeyedService,
   // Returns a display name for an origin in the process id, to be used in
   // permission infobar or on the frame of the notification toast.  Different
   // from the origin itself when dealing with extensions.
-  string16 DisplayNameForOriginInProcessId(const GURL& origin, int process_id);
+  base::string16 DisplayNameForOriginInProcessId(const GURL& origin,
+                                                 int process_id);
 
   // Notifies the observers when permissions settings change.
   void NotifySettingsChange();