Rewrite std::string("") to std::string(), Linux edition.

This patch was generated by running the empty_string clang tool
across the Chromium Linux compilation database. Implicitly or
explicitly constructing std::string() with a "" argument is
inefficient as the caller needs to emit extra instructions to
pass an argument, and the constructor needlessly copies a byte
into internal storage. Rewriting these instances to simply call
the default constructor appears to save ~14-18 kilobytes on an
optimized release build.

BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=193020

Review URL: https://codereview.chromium.org/13145003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193040 0039d316-1c4b-4281-b951-d872f2087c98

43 files changed, 326 insertions, 226 deletions

diff --git a/chrome/browser/ui/app_list/app_list_service.cc b/chrome/browser/ui/app_list/app_list_service.cc
index f02da1e..a0bf010 100644
--- a/chrome/browser/ui/app_list/app_list_service.cc
+++ b/chrome/browser/ui/app_list/app_list_service.cc
@@ -66,7 +66,7 @@ void AppListService::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterIntegerPref(prefs::kAppListLaunchCount, 0);
   registry->RegisterInt64Pref(prefs::kLastAppListAppLaunchPing, 0);
   registry->RegisterIntegerPref(prefs::kAppListAppLaunchCount, 0);
-  registry->RegisterStringPref(prefs::kAppListProfile, "");
+  registry->RegisterStringPref(prefs::kAppListProfile, std::string());
 #if defined(OS_WIN)
   registry->RegisterBooleanPref(prefs::kRestartWithAppList, false);
 #endif
diff --git a/chrome/browser/ui/blocked_content/blocked_content_tab_helper.cc b/chrome/browser/ui/blocked_content/blocked_content_tab_helper.cc
index 2ee22c3..844f210 100644
--- a/chrome/browser/ui/blocked_content/blocked_content_tab_helper.cc
+++ b/chrome/browser/ui/blocked_content/blocked_content_tab_helper.cc
@@ -110,10 +110,8 @@ void BlockedContentTabHelper::AddPopup(content::WebContents* new_contents,
 
   if (creator.is_valid() &&
       profile->GetHostContentSettingsMap()->GetContentSetting(
-          creator,
-          creator,
-          CONTENT_SETTINGS_TYPE_POPUPS,
-          "") == CONTENT_SETTING_ALLOW) {
+          creator, creator, CONTENT_SETTINGS_TYPE_POPUPS, std::string()) ==
+          CONTENT_SETTING_ALLOW) {
     content::WebContentsDelegate* delegate = web_contents()->GetDelegate();
     if (delegate) {
       delegate->AddNewContents(web_contents(),
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 47f07ca..a31b4b0 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -813,9 +813,13 @@ void Browser::OpenFile() {
   ui::SelectFileDialog::FileTypeInfo file_types;
   file_types.support_drive = true;
   select_file_dialog_->SelectFile(ui::SelectFileDialog::SELECT_OPEN_FILE,
-                                  string16(), directory,
-                                  &file_types, 0, FILE_PATH_LITERAL(""),
-                                  parent_window, NULL);
+                                  string16(),
+                                  directory,
+                                  &file_types,
+                                  0,
+                                  base::FilePath::StringType(),
+                                  parent_window,
+                                  NULL);
 }
 
 void Browser::UpdateDownloadShelfVisibility(bool visible) {
diff --git a/chrome/browser/ui/browser_browsertest.cc b/chrome/browser/ui/browser_browsertest.cc
index 5e6b769..e253102 100644
--- a/chrome/browser/ui/browser_browsertest.cc
+++ b/chrome/browser/ui/browser_browsertest.cc
@@ -558,7 +558,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, NullOpenerRedirectForksProcess) {
                                     base::FilePath(kDocRoot));
   ASSERT_TRUE(https_test_server.Start());
   GURL http_url(test_server()->GetURL("files/title1.html"));
-  GURL https_url(https_test_server.GetURL(""));
+  GURL https_url(https_test_server.GetURL(std::string()));
 
   // Start with an http URL.
   ui_test_utils::NavigateToURL(browser(), http_url);
@@ -647,7 +647,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, OtherRedirectsDontForkProcess) {
                                     base::FilePath(kDocRoot));
   ASSERT_TRUE(https_test_server.Start());
   GURL http_url(test_server()->GetURL("files/title1.html"));
-  GURL https_url(https_test_server.GetURL(""));
+  GURL https_url(https_test_server.GetURL(std::string()));
 
   // Start with an http URL.
   ui_test_utils::NavigateToURL(browser(), http_url);
@@ -747,7 +747,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, CommandCreateAppShortcutHttp) {
       browser()->command_controller()->command_updater();
 
   ASSERT_TRUE(test_server()->Start());
-  GURL http_url(test_server()->GetURL(""));
+  GURL http_url(test_server()->GetURL(std::string()));
   ASSERT_TRUE(http_url.SchemeIs(chrome::kHttpScheme));
   ui_test_utils::NavigateToURL(browser(), http_url);
   EXPECT_TRUE(command_updater->IsCommandEnabled(IDC_CREATE_SHORTCUTS));
@@ -775,7 +775,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, CommandCreateAppShortcutFtp) {
                               net::TestServer::kLocalhost,
                               base::FilePath(kDocRoot));
   ASSERT_TRUE(test_server.Start());
-  GURL ftp_url(test_server.GetURL(""));
+  GURL ftp_url(test_server.GetURL(std::string()));
   ASSERT_TRUE(ftp_url.SchemeIs(chrome::kFtpScheme));
   ui_test_utils::NavigateToURL(browser(), ftp_url);
   EXPECT_TRUE(command_updater->IsCommandEnabled(IDC_CREATE_SHORTCUTS));
@@ -807,7 +807,7 @@ IN_PROC_BROWSER_TEST_F(BrowserTest, CommandCreateAppShortcutInvalid) {
 // DISABLED: http://crbug.com/72310
 IN_PROC_BROWSER_TEST_F(BrowserTest, DISABLED_ConvertTabToAppShortcut) {
   ASSERT_TRUE(test_server()->Start());
-  GURL http_url(test_server()->GetURL(""));
+  GURL http_url(test_server()->GetURL(std::string()));
   ASSERT_TRUE(http_url.SchemeIs(chrome::kHttpScheme));
 
   ASSERT_EQ(1, browser()->tab_strip_model()->count());
diff --git a/chrome/browser/ui/browser_tab_contents.cc b/chrome/browser/ui/browser_tab_contents.cc
index c4fe56c..fdcaa16 100644
--- a/chrome/browser/ui/browser_tab_contents.cc
+++ b/chrome/browser/ui/browser_tab_contents.cc
@@ -172,8 +172,10 @@ void BrowserTabContents::AttachTabHelpers(WebContents* web_contents) {
   // because the connected state may change while this tab is open.  Having a
   // one-click signin helper attached does not cause problems if the profile
   // happens to be already connected.
-  if (OneClickSigninHelper::CanOffer(
-          web_contents, OneClickSigninHelper::CAN_OFFER_FOR_ALL, "", NULL)) {
+  if (OneClickSigninHelper::CanOffer(web_contents,
+                                     OneClickSigninHelper::CAN_OFFER_FOR_ALL,
+                                     std::string(),
+                                     NULL)) {
     OneClickSigninHelper::CreateForWebContents(web_contents);
   }
 #endif
diff --git a/chrome/browser/ui/browser_tabrestore.cc b/chrome/browser/ui/browser_tabrestore.cc
index 0e96e0d..373de5c 100644
--- a/chrome/browser/ui/browser_tabrestore.cc
+++ b/chrome/browser/ui/browser_tabrestore.cc
@@ -50,7 +50,7 @@ WebContents* CreateRestoredTab(
   // session_storage_namespace.h include since we only need that to assign
   // into the map.
   content::SessionStorageNamespaceMap session_storage_namespace_map;
-  session_storage_namespace_map[""] = session_storage_namespace;
+  session_storage_namespace_map[std::string()] = session_storage_namespace;
   WebContents::CreateParams create_params(
       browser->profile(),
       tab_util::GetSiteInstanceForNewTab(browser->profile(), restore_url));
diff --git a/chrome/browser/ui/certificate_dialogs.cc b/chrome/browser/ui/certificate_dialogs.cc
index 8e69b5d..939c3a13 100644
--- a/chrome/browser/ui/certificate_dialogs.cc
+++ b/chrome/browser/ui/certificate_dialogs.cc
@@ -52,7 +52,7 @@ std::string GetBase64String(net::X509Certificate::OSCertHandle cert) {
   if (!base::Base64Encode(
       x509_certificate_model::GetDerString(cert), &base64)) {
     LOG(ERROR) << "base64 encoding error";
-    return "";
+    return std::string();
   }
   return "-----BEGIN CERTIFICATE-----\r\n" +
       WrapAt64(base64) +
diff --git a/chrome/browser/ui/chrome_pages.cc b/chrome/browser/ui/chrome_pages.cc
index fe9300c..7fed38a 100644
--- a/chrome/browser/ui/chrome_pages.cc
+++ b/chrome/browser/ui/chrome_pages.cc
@@ -65,7 +65,7 @@ void ShowBookmarkManager(Browser* browser) {
 }
 
 void ShowBookmarkManagerForNode(Browser* browser, int64 node_id) {
-  OpenBookmarkManagerWithHash(browser, "", node_id);
+  OpenBookmarkManagerWithHash(browser, std::string(), node_id);
 }
 
 void ShowHistory(Browser* browser) {
diff --git a/chrome/browser/ui/chrome_select_file_policy_unittest.cc b/chrome/browser/ui/chrome_select_file_policy_unittest.cc
index d5a6c10..8b5ca82 100644
--- a/chrome/browser/ui/chrome_select_file_policy_unittest.cc
+++ b/chrome/browser/ui/chrome_select_file_policy_unittest.cc
@@ -56,7 +56,7 @@ class FileSelectionUser : public ui::SelectFileDialog::Listener {
                                     file_path,
                                     NULL,
                                     0,
-                                    FILE_PATH_LITERAL(""),
+                                    base::FilePath::StringType(),
                                     NULL,
                                     NULL);
     file_selection_initialisation_in_progress = false;
diff --git a/chrome/browser/ui/fullscreen/fullscreen_controller_state_test.cc b/chrome/browser/ui/fullscreen/fullscreen_controller_state_test.cc
index 34bb7f0..3c851f4 100644
--- a/chrome/browser/ui/fullscreen/fullscreen_controller_state_test.cc
+++ b/chrome/browser/ui/fullscreen/fullscreen_controller_state_test.cc
@@ -658,7 +658,7 @@ FullscreenControllerStateTest::StateTransitionInfo
 std::string FullscreenControllerStateTest::GetAndClearDebugLog() {
   debugging_log_ << "(End of Debugging Log)\n";
   std::string output_log = "\nDebugging Log:\n" + debugging_log_.str();
-  debugging_log_.str("");
+  debugging_log_.str(std::string());
   return output_log;
 }
 
diff --git a/chrome/browser/ui/gtk/bookmarks/bookmark_utils_gtk.cc b/chrome/browser/ui/gtk/bookmarks/bookmark_utils_gtk.cc
index 3796706..a4d0a2b 100644
--- a/chrome/browser/ui/gtk/bookmarks/bookmark_utils_gtk.cc
+++ b/chrome/browser/ui/gtk/bookmarks/bookmark_utils_gtk.cc
@@ -462,7 +462,12 @@ bool CreateNewBookmarkFromNetscapeURL(GtkSelectionData* selection_data,
 
 string16 GetNameForURL(const GURL& url) {
   if (url.is_valid()) {
-    return net::GetSuggestedFilename(url, "", "", "", "", std::string());
+    return net::GetSuggestedFilename(url,
+                                     std::string(),
+                                     std::string(),
+                                     std::string(),
+                                     std::string(),
+                                     std::string());
   } else {
     return l10n_util::GetStringUTF16(IDS_APP_UNTITLED_SHORTCUT_FILE_NAME);
   }
diff --git a/chrome/browser/ui/gtk/constrained_web_dialog_delegate_gtk.cc b/chrome/browser/ui/gtk/constrained_web_dialog_delegate_gtk.cc
index fe42588..fdb10b5 100644
--- a/chrome/browser/ui/gtk/constrained_web_dialog_delegate_gtk.cc
+++ b/chrome/browser/ui/gtk/constrained_web_dialog_delegate_gtk.cc
@@ -127,7 +127,7 @@ ConstrainedWebDialogDelegateViewGtk::ConstrainedWebDialogDelegateViewGtk(
 
 void ConstrainedWebDialogDelegateViewGtk::OnDestroy(GtkWidget* widget) {
   if (!impl_->closed_via_webui())
-    GetWebDialogDelegate()->OnDialogClosed("");
+    GetWebDialogDelegate()->OnDialogClosed(std::string());
   delete this;
 }
 
diff --git a/chrome/browser/ui/gtk/first_run_bubble.cc b/chrome/browser/ui/gtk/first_run_bubble.cc
index 7207758..70bf245 100644
--- a/chrome/browser/ui/gtk/first_run_bubble.cc
+++ b/chrome/browser/ui/gtk/first_run_bubble.cc
@@ -44,10 +44,12 @@ FirstRunBubble::FirstRunBubble(Browser* browser,
     : browser_(browser),
       bubble_(NULL) {
   GtkThemeService* theme_service = GtkThemeService::GetFrom(browser->profile());
-  GtkWidget* title = theme_service->BuildLabel("", ui::kGdkBlack);
-  char* markup = g_markup_printf_escaped(kSearchLabelMarkup,
+  GtkWidget* title = theme_service->BuildLabel(std::string(), ui::kGdkBlack);
+  char* markup = g_markup_printf_escaped(
+      kSearchLabelMarkup,
       l10n_util::GetStringFUTF8(IDS_FR_BUBBLE_TITLE,
-          GetDefaultSearchEngineName(browser->profile())).c_str());
+                                GetDefaultSearchEngineName(browser->profile()))
+          .c_str());
   gtk_label_set_markup(GTK_LABEL(title), markup);
   g_free(markup);
 
diff --git a/chrome/browser/ui/gtk/location_bar_view_gtk.cc b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
index befcd30..9bd0ebb 100644
--- a/chrome/browser/ui/gtk/location_bar_view_gtk.cc
+++ b/chrome/browser/ui/gtk/location_bar_view_gtk.cc
@@ -410,9 +410,9 @@ void LocationBarViewGtk::Init(bool popup_window_mode) {
 
   // Tab to search (the keyword box on the left hand side).
   tab_to_search_full_label_ =
-      theme_service_->BuildLabel("", ui::kGdkBlack);
+      theme_service_->BuildLabel(std::string(), ui::kGdkBlack);
   tab_to_search_partial_label_ =
-      theme_service_->BuildLabel("", ui::kGdkBlack);
+      theme_service_->BuildLabel(std::string(), ui::kGdkBlack);
   GtkWidget* tab_to_search_label_hbox = gtk_hbox_new(FALSE, 0);
   gtk_box_pack_start(GTK_BOX(tab_to_search_label_hbox),
                      tab_to_search_full_label_, FALSE, FALSE, 0);
@@ -458,12 +458,12 @@ void LocationBarViewGtk::Init(bool popup_window_mode) {
   tab_to_search_hint_ = gtk_hbox_new(FALSE, 0);
   gtk_widget_set_name(tab_to_search_hint_, "chrome-tab-to-search-hint");
   tab_to_search_hint_leading_label_ =
-      theme_service_->BuildLabel("", kHintTextColor);
+      theme_service_->BuildLabel(std::string(), kHintTextColor);
   gtk_widget_set_sensitive(tab_to_search_hint_leading_label_, FALSE);
   tab_to_search_hint_icon_ = gtk_image_new_from_pixbuf(
       rb.GetNativeImageNamed(IDR_LOCATION_BAR_KEYWORD_HINT_TAB).ToGdkPixbuf());
   tab_to_search_hint_trailing_label_ =
-      theme_service_->BuildLabel("", kHintTextColor);
+      theme_service_->BuildLabel(std::string(), kHintTextColor);
   gtk_widget_set_sensitive(tab_to_search_hint_trailing_label_, FALSE);
   gtk_box_pack_start(GTK_BOX(tab_to_search_hint_),
                      tab_to_search_hint_leading_label_,
diff --git a/chrome/browser/ui/gtk/ssl_client_certificate_selector.cc b/chrome/browser/ui/gtk/ssl_client_certificate_selector.cc
index ebf2e78..d96e1d2 100644
--- a/chrome/browser/ui/gtk/ssl_client_certificate_selector.cc
+++ b/chrome/browser/ui/gtk/ssl_client_certificate_selector.cc
@@ -249,7 +249,7 @@ std::string SSLClientCertificateSelector::FormatComboBoxText(
     net::X509Certificate::OSCertHandle cert, const std::string& nickname) {
   std::string rv(nickname);
   rv += " [";
-  rv += x509_certificate_model::GetSerialNumberHexified(cert, "");
+  rv += x509_certificate_model::GetSerialNumberHexified(cert, std::string());
   rv += ']';
   return rv;
 }
@@ -266,8 +266,8 @@ std::string SSLClientCertificateSelector::FormatDetailsText(
   rv += "\n  ";
   rv += l10n_util::GetStringFUTF8(
       IDS_CERT_SERIAL_NUMBER_FORMAT,
-      UTF8ToUTF16(
-          x509_certificate_model::GetSerialNumberHexified(cert, "")));
+      UTF8ToUTF16(x509_certificate_model::GetSerialNumberHexified(
+          cert, std::string())));
 
   base::Time issued, expires;
   if (x509_certificate_model::GetTimes(cert, &issued, &expires)) {
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.cc b/chrome/browser/ui/prefs/prefs_tab_helper.cc
index b629064..7056161 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.cc
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.cc
@@ -152,7 +152,7 @@ ALL_FONT_SCRIPTS(WEBKIT_WEBPREFS_FONTS_STANDARD)
       // We haven't already set a default value for this font preference, so set
       // an empty string as the default.
       registry->RegisterStringPref(
-          pref_name, "", PrefRegistrySyncable::UNSYNCABLE_PREF);
+          pref_name, std::string(), PrefRegistrySyncable::UNSYNCABLE_PREF);
     }
   }
 }
@@ -587,7 +587,7 @@ void PrefsTabHelper::RegisterUserPrefs(PrefRegistrySyncable* registry) {
                                         IDS_STATIC_ENCODING_LIST,
                                         PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterStringPref(prefs::kRecentlySelectedEncoding,
-                               "",
+                               std::string(),
                                PrefRegistrySyncable::UNSYNCABLE_PREF);
 
   RegisterPrefsToMigrate(registry);
@@ -666,7 +666,7 @@ void PrefsTabHelper::OnWebPrefChanged(const std::string& pref_name) {
     if (pref_value.empty()) {
       WebPreferences web_prefs =
           web_contents_->GetRenderViewHost()->GetWebkitPreferences();
-      OverrideFontFamily(&web_prefs, generic_family, script, "");
+      OverrideFontFamily(&web_prefs, generic_family, script, std::string());
       web_contents_->GetRenderViewHost()->UpdateWebkitPreferences(web_prefs);
       return;
     }
diff --git a/chrome/browser/ui/search/instant_browsertest.cc b/chrome/browser/ui/search/instant_browsertest.cc
index 6afe15b..2e4beb2 100644
--- a/chrome/browser/ui/search/instant_browsertest.cc
+++ b/chrome/browser/ui/search/instant_browsertest.cc
@@ -607,7 +607,7 @@ IN_PROC_BROWSER_TEST_F(InstantTest, PageVisibility) {
   EXPECT_TRUE(CheckVisibilityIs(overlay, true));
 
   // Deleting the omnibox text should hide the overlay.
-  SetOmniboxText("");
+  SetOmniboxText(std::string());
   EXPECT_TRUE(CheckVisibilityIs(active_tab, true));
   EXPECT_TRUE(CheckVisibilityIs(overlay, false));
 
diff --git a/chrome/browser/ui/startup/startup_browser_creator_impl.cc b/chrome/browser/ui/startup/startup_browser_creator_impl.cc
index 7600026..1d0cff3 100644
--- a/chrome/browser/ui/startup/startup_browser_creator_impl.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator_impl.cc
@@ -933,8 +933,8 @@ void StartupBrowserCreatorImpl::AddStartupURLs(
                          GURL(std::string(chrome::kChromeUISettingsURL) +
                               chrome::kManagedUserSettingsSubPage));
     if (has_reset_local_passphrase_switch) {
-      prefs->SetString(prefs::kManagedModeLocalPassphrase, "");
-      prefs->SetString(prefs::kManagedModeLocalSalt, "");
+      prefs->SetString(prefs::kManagedModeLocalPassphrase, std::string());
+      prefs->SetString(prefs::kManagedModeLocalSalt, std::string());
     }
   }
 
diff --git a/chrome/browser/ui/sync/one_click_signin_helper_unittest.cc b/chrome/browser/ui/sync/one_click_signin_helper_unittest.cc
index e879b6e..4892ab6 100644
--- a/chrome/browser/ui/sync/one_click_signin_helper_unittest.cc
+++ b/chrome/browser/ui/sync/one_click_signin_helper_unittest.cc
@@ -389,13 +389,15 @@ TEST_F(OneClickSigninHelperTest, CanOfferNoContents) {
       "user@gmail.com", &error_message));
   EXPECT_EQ("", error_message);
   EXPECT_FALSE(OneClickSigninHelper::CanOffer(
-      NULL, OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-      "", &error_message));
+      NULL,
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
   EXPECT_EQ("", error_message);
 }
 
 TEST_F(OneClickSigninHelperTest, CanOffer) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
         WillRepeatedly(Return(true));
@@ -408,9 +410,10 @@ TEST_F(OneClickSigninHelperTest, CanOffer) {
       web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_ALL,
       "user@gmail.com", NULL));
   EXPECT_TRUE(OneClickSigninHelper::CanOffer(
-                  web_contents(),
-                  OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-                  "", NULL));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      NULL));
 
   EnableOneClick(false);
 
@@ -424,14 +427,15 @@ TEST_F(OneClickSigninHelperTest, CanOffer) {
       web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_ALL,
       "user@gmail.com", &error_message));
   EXPECT_FALSE(OneClickSigninHelper::CanOffer(
-                  web_contents(),
-                  OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-                  "", &error_message));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
   EXPECT_EQ("", error_message);
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferFirstSetup) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
         WillRepeatedly(Return(true));
@@ -454,8 +458,10 @@ TEST_F(OneClickSigninHelperTest, CanOfferFirstSetup) {
       OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
       "foo@gmail.com", NULL));
   EXPECT_TRUE(OneClickSigninHelper::CanOffer(
-      web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-      "", NULL));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      NULL));
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferProfileConnected) {
@@ -492,12 +498,14 @@ TEST_F(OneClickSigninHelperTest, CanOfferProfileConnected) {
                                       UTF8ToUTF16("foo@gmail.com")),
             error_message);
   EXPECT_TRUE(OneClickSigninHelper::CanOffer(
-      web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-      "", &error_message));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferUsernameNotAllowed) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
       WillRepeatedly(Return(false));
@@ -513,16 +521,15 @@ TEST_F(OneClickSigninHelperTest, CanOfferUsernameNotAllowed) {
       "foo@gmail.com", &error_message));
   EXPECT_EQ(l10n_util::GetStringUTF8(IDS_SYNC_LOGIN_NAME_PROHIBITED),
             error_message);
-  EXPECT_TRUE(
-      OneClickSigninHelper::CanOffer(
-          web_contents(),
-          OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-          "",
-          &error_message));
+  EXPECT_TRUE(OneClickSigninHelper::CanOffer(
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferWithRejectedEmail) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
         WillRepeatedly(Return(true));
@@ -551,7 +558,7 @@ TEST_F(OneClickSigninHelperTest, CanOfferWithRejectedEmail) {
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferIncognito) {
-  CreateSigninManager(true, "");
+  CreateSigninManager(true, std::string());
 
   std::string error_message;
   EXPECT_FALSE(OneClickSigninHelper::CanOffer(
@@ -563,13 +570,15 @@ TEST_F(OneClickSigninHelperTest, CanOfferIncognito) {
       "user@gmail.com", &error_message));
   EXPECT_EQ("", error_message);
   EXPECT_FALSE(OneClickSigninHelper::CanOffer(
-      web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-      "", &error_message));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
   EXPECT_EQ("", error_message);
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferNoSigninCookies) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
   AllowSigninCookies(false);
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
@@ -585,8 +594,10 @@ TEST_F(OneClickSigninHelperTest, CanOfferNoSigninCookies) {
       "user@gmail.com", &error_message));
   EXPECT_EQ("", error_message);
   EXPECT_FALSE(OneClickSigninHelper::CanOffer(
-      web_contents(), OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
-      "", &error_message));
+      web_contents(),
+      OneClickSigninHelper::CAN_OFFER_FOR_INTERSTITAL_ONLY,
+      std::string(),
+      &error_message));
   EXPECT_EQ("", error_message);
 }
 
@@ -595,7 +606,7 @@ TEST_F(OneClickSigninHelperTest, CanOfferUntrustedProcess) {
   ASSERT_NE(trusted.GetID(), process()->GetID());
   // Make sure the RenderProcessHost used by the test is untrusted.
   SetTrustedSigninProcessID(trusted.GetID());
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
         WillRepeatedly(Return(true));
@@ -607,7 +618,7 @@ TEST_F(OneClickSigninHelperTest, CanOfferUntrustedProcess) {
 }
 
 TEST_F(OneClickSigninHelperTest, CanOfferDisabledByPolicy) {
-  CreateSigninManager(false, "");
+  CreateSigninManager(false, std::string());
 
   EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
         WillRepeatedly(Return(true));
@@ -642,7 +653,7 @@ TEST_F(OneClickSigninHelperTest, CanOfferDisabledByPolicy) {
 // Should not crash if a helper instance is not associated with an incognito
 // web contents.
 TEST_F(OneClickSigninHelperTest, ShowInfoBarUIThreadIncognito) {
-  CreateSigninManager(true, "");
+  CreateSigninManager(true, std::string());
   OneClickSigninHelper* helper =
       OneClickSigninHelper::FromWebContents(web_contents());
   EXPECT_EQ(NULL, helper);
@@ -657,9 +668,9 @@ TEST_F(OneClickSigninHelperTest, ShowInfoBarUIThreadIncognito) {
 // config sync, then Chrome should redirect immidiately to sync settings page,
 // and upon successful setup, redirect back to webstore.
 TEST_F(OneClickSigninHelperTest, SigninFromWebstoreWithConfigSyncfirst) {
-  CreateSigninManager(false, "");
-  EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
-        WillRepeatedly(Return(true));
+  CreateSigninManager(false, std::string());
+  EXPECT_CALL(*signin_manager_, IsAllowedUsername(_))
+      .WillRepeatedly(Return(true));
 
   CreateProfileSyncServiceMock();
 
@@ -687,9 +698,9 @@ TEST_F(OneClickSigninHelperTest, SigninFromWebstoreWithConfigSyncfirst) {
 }
 
 TEST_F(OneClickSigninHelperTest, ShowSigninBubbleAfterSigninComplete) {
-  CreateSigninManager(false, "");
-  EXPECT_CALL(*signin_manager_, IsAllowedUsername(_)).
-        WillRepeatedly(Return(true));
+  CreateSigninManager(false, std::string());
+  EXPECT_CALL(*signin_manager_, IsAllowedUsername(_))
+      .WillRepeatedly(Return(true));
 
   CreateProfileSyncServiceMock();
 
@@ -725,31 +736,34 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThread) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::CAN_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadIncognito) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(true));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadNoIOData) {
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, NULL));
+                valid_gaia_url_, std::string(), &request_, NULL));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadBadURL) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
+  EXPECT_EQ(
+      OneClickSigninHelper::IGNORE_REQUEST,
+      OneClickSigninHelper::CanOfferOnIOThreadImpl(
+          GURL("https://foo.com/"), std::string(), &request_, io_data.get()));
   EXPECT_EQ(OneClickSigninHelper::IGNORE_REQUEST,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                GURL("https://foo.com/"), "", &request_, io_data.get()));
-  EXPECT_EQ(OneClickSigninHelper::IGNORE_REQUEST,
-            OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                GURL("http://accounts.google.com/"), "",
-                &request_, io_data.get()));
+                GURL("http://accounts.google.com/"),
+                std::string(),
+                &request_,
+                io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadReferrer) {
@@ -796,7 +810,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadDisabled) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadSignedIn) {
@@ -806,7 +820,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadSignedIn) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadEmailNotAllowed) {
@@ -814,7 +828,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadEmailNotAllowed) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadEmailAlreadyUsed) {
@@ -827,7 +841,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadEmailAlreadyUsed) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadWithRejectedEmail) {
@@ -835,7 +849,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadWithRejectedEmail) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadNoSigninCookies) {
@@ -843,14 +857,14 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadNoSigninCookies) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
 
 TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadDisabledByPolicy) {
   scoped_ptr<TestProfileIOData> io_data(CreateTestProfileIOData(false));
   EXPECT_EQ(OneClickSigninHelper::CAN_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 
   // Simulate a policy disabling signin by writing kSigninAllowed directly.
   // We should not offer to sign in the browser.
@@ -858,7 +872,7 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadDisabledByPolicy) {
       prefs::kSigninAllowed, base::Value::CreateBooleanValue(false));
   EXPECT_EQ(OneClickSigninHelper::DONT_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 
   // Reset the preference.
   profile_->GetTestingPrefService()->SetManagedPref(
@@ -870,5 +884,5 @@ TEST_F(OneClickSigninHelperIOTest, CanOfferOnIOThreadDisabledByPolicy) {
       prefs::kSyncManaged, base::Value::CreateBooleanValue(true));
   EXPECT_EQ(OneClickSigninHelper::CAN_OFFER,
             OneClickSigninHelper::CanOfferOnIOThreadImpl(
-                valid_gaia_url_, "", &request_, io_data.get()));
+                valid_gaia_url_, std::string(), &request_, io_data.get()));
 }
diff --git a/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc b/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
index 4b003cf..4115f18 100644
--- a/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
+++ b/chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc
@@ -43,7 +43,7 @@ Profile* TabContentsSyncedTabDelegate::profile() const {
 std::string TabContentsSyncedTabDelegate::GetExtensionAppId() const {
   const scoped_refptr<const extensions::Extension> extension_app(
       extensions::TabHelper::FromWebContents(web_contents_)->extension_app());
-  return (extension_app.get() ? extension_app->id() : "");
+  return (extension_app.get() ? extension_app->id() : std::string());
 }
 
 int TabContentsSyncedTabDelegate::GetCurrentEntryIndex() const {
diff --git a/chrome/browser/ui/website_settings/website_settings.cc b/chrome/browser/ui/website_settings/website_settings.cc
index daf7257..8a37c39 100644
--- a/chrome/browser/ui/website_settings/website_settings.cc
+++ b/chrome/browser/ui/website_settings/website_settings.cc
@@ -143,12 +143,18 @@ void WebsiteSettings::OnSitePermissionChanged(ContentSettingsType type,
       secondary_pattern = ContentSettingsPattern::Wildcard();
       // Set permission for both microphone and camera.
       content_settings_->SetContentSetting(
-          primary_pattern, secondary_pattern,
-          CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC, "", setting);
+          primary_pattern,
+          secondary_pattern,
+          CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
+          std::string(),
+          setting);
 
       content_settings_->SetContentSetting(
-          primary_pattern, secondary_pattern,
-          CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA, "", setting);
+          primary_pattern,
+          secondary_pattern,
+          CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
+          std::string(),
+          setting);
       break;
     }
     default:
@@ -167,7 +173,7 @@ void WebsiteSettings::OnSitePermissionChanged(ContentSettingsType type,
     // can not create media settings exceptions by hand.
     content_settings::SettingInfo info;
     scoped_ptr<Value> v(content_settings_->GetWebsiteSetting(
-        site_url_, site_url_, type, "", &info));
+        site_url_, site_url_, type, std::string(), &info));
     DCHECK(info.source == content_settings::SETTING_SOURCE_USER);
     ContentSettingsPattern::Relation r1 =
         info.primary_pattern.Compare(primary_pattern);
@@ -188,7 +194,7 @@ void WebsiteSettings::OnSitePermissionChanged(ContentSettingsType type,
     if (setting != CONTENT_SETTING_DEFAULT)
       value = Value::CreateIntegerValue(setting);
     content_settings_->SetWebsiteSetting(
-        primary_pattern, secondary_pattern, type, "", value);
+        primary_pattern, secondary_pattern, type, std::string(), value);
   }
 
   show_info_bar_ = true;
@@ -452,14 +458,20 @@ void WebsiteSettings::PresentSitePermissions() {
     content_settings::SettingInfo info;
     if (permission_info.type == CONTENT_SETTINGS_TYPE_MEDIASTREAM) {
       scoped_ptr<base::Value> mic_value(content_settings_->GetWebsiteSetting(
-          site_url_, site_url_, CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
-          "", &info));
+          site_url_,
+          site_url_,
+          CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
+          std::string(),
+          &info));
       ContentSetting mic_setting =
           content_settings::ValueToContentSetting(mic_value.get());
 
       scoped_ptr<base::Value> camera_value(content_settings_->GetWebsiteSetting(
-          site_url_, site_url_, CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
-          "", &info));
+          site_url_,
+          site_url_,
+          CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
+          std::string(),
+          &info));
       ContentSetting camera_setting =
           content_settings::ValueToContentSetting(camera_value.get());
 
@@ -469,7 +481,7 @@ void WebsiteSettings::PresentSitePermissions() {
         permission_info.setting = mic_setting;
     } else {
       scoped_ptr<Value> value(content_settings_->GetWebsiteSetting(
-          site_url_, site_url_, permission_info.type, "", &info));
+          site_url_, site_url_, permission_info.type, std::string(), &info));
       DCHECK(value.get());
       if (value->GetType() == Value::TYPE_INTEGER) {
         permission_info.setting =
diff --git a/chrome/browser/ui/website_settings/website_settings_unittest.cc b/chrome/browser/ui/website_settings/website_settings_unittest.cc
index 4fe881a..8f486af 100644
--- a/chrome/browser/ui/website_settings/website_settings_unittest.cc
+++ b/chrome/browser/ui/website_settings/website_settings_unittest.cc
@@ -165,22 +165,22 @@ TEST_F(WebsiteSettingsTest, OnPermissionsChanged) {
   HostContentSettingsMap* content_settings =
       profile()->GetHostContentSettingsMap();
   ContentSetting setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_POPUPS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_POPUPS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_BLOCK);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_PLUGINS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_PLUGINS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_GEOLOCATION, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_GEOLOCATION, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ASK);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_NOTIFICATIONS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_NOTIFICATIONS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ASK);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ASK);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ASK);
 
   EXPECT_CALL(*mock_ui(), SetIdentityInfo(_));
@@ -212,22 +212,22 @@ TEST_F(WebsiteSettingsTest, OnPermissionsChanged) {
 
   // Verify that the site permissions were changed correctly.
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_POPUPS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_POPUPS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_PLUGINS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_PLUGINS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_BLOCK);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_GEOLOCATION, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_GEOLOCATION, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_NOTIFICATIONS, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_NOTIFICATIONS, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
   setting = content_settings->GetContentSetting(
-      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA, "");
+      url(), url(), CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA, std::string());
   EXPECT_EQ(setting, CONTENT_SETTING_ALLOW);
 }
 
diff --git a/chrome/browser/ui/webui/about_ui.cc b/chrome/browser/ui/webui/about_ui.cc
index 861d2be..b2dc2ae 100644
--- a/chrome/browser/ui/webui/about_ui.cc
+++ b/chrome/browser/ui/webui/about_ui.cc
@@ -785,15 +785,21 @@ std::string AboutSandbox() {
 
   data.append("<table>");
 
-  AboutSandboxRow(&data, "", IDS_ABOUT_SANDBOX_SUID_SANDBOX,
+  AboutSandboxRow(&data,
+                  std::string(),
+                  IDS_ABOUT_SANDBOX_SUID_SANDBOX,
                   status & content::kSandboxLinuxSUID);
   AboutSandboxRow(&data, "&nbsp;&nbsp;", IDS_ABOUT_SANDBOX_PID_NAMESPACES,
                   status & content::kSandboxLinuxPIDNS);
   AboutSandboxRow(&data, "&nbsp;&nbsp;", IDS_ABOUT_SANDBOX_NET_NAMESPACES,
                   status & content::kSandboxLinuxNetNS);
-  AboutSandboxRow(&data, "", IDS_ABOUT_SANDBOX_SECCOMP_LEGACY_SANDBOX,
+  AboutSandboxRow(&data,
+                  std::string(),
+                  IDS_ABOUT_SANDBOX_SECCOMP_LEGACY_SANDBOX,
                   status & content::kSandboxLinuxSeccompLegacy);
-  AboutSandboxRow(&data, "", IDS_ABOUT_SANDBOX_SECCOMP_BPF_SANDBOX,
+  AboutSandboxRow(&data,
+                  std::string(),
+                  IDS_ABOUT_SANDBOX_SECCOMP_BPF_SANDBOX,
                   status & content::kSandboxLinuxSeccompBpf);
 
   data.append("</table>");
diff --git a/chrome/browser/ui/webui/downloads_dom_handler_browsertest.cc b/chrome/browser/ui/webui/downloads_dom_handler_browsertest.cc
index 0bfa286..19e6404 100644
--- a/chrome/browser/ui/webui/downloads_dom_handler_browsertest.cc
+++ b/chrome/browser/ui/webui/downloads_dom_handler_browsertest.cc
@@ -147,7 +147,7 @@ IN_PROC_BROWSER_TEST_F(DownloadsDOMHandlerTest,
       base::FilePath(FILE_PATH_LITERAL("/path/to/file")),
       base::FilePath(FILE_PATH_LITERAL("/path/to/file")),
       url_chain,
-      GURL(""),
+      GURL(std::string()),
       current,
       current,
       128,
diff --git a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
index bd3bc6f..11ea684 100644
--- a/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
+++ b/chrome/browser/ui/webui/extensions/extension_settings_handler.cc
@@ -930,9 +930,14 @@ void ExtensionSettingsHandler::HandleLoadUnpackedExtensionMessage(
   load_extension_dialog_ = ui::SelectFileDialog::Create(
       this, new ChromeSelectFilePolicy(web_ui()->GetWebContents()));
   load_extension_dialog_->SelectFile(
-      kSelectType, select_title, last_unpacked_directory_, NULL,
-      kFileTypeIndex, FILE_PATH_LITERAL(""),
-      web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow(), NULL);
+      kSelectType,
+      select_title,
+      last_unpacked_directory_,
+      NULL,
+      kFileTypeIndex,
+      base::FilePath::StringType(),
+      web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow(),
+      NULL);
 }
 
 void ExtensionSettingsHandler::ShowAlert(const std::string& message) {
diff --git a/chrome/browser/ui/webui/extensions/pack_extension_handler.cc b/chrome/browser/ui/webui/extensions/pack_extension_handler.cc
index a69cd4d..d201c91 100644
--- a/chrome/browser/ui/webui/extensions/pack_extension_handler.cc
+++ b/chrome/browser/ui/webui/extensions/pack_extension_handler.cc
@@ -184,8 +184,12 @@ void PackExtensionHandler::HandleSelectFilePathMessage(
   load_extension_dialog_ = ui::SelectFileDialog::Create(
       this, new ChromeSelectFilePolicy(web_ui()->GetWebContents()));
   load_extension_dialog_->SelectFile(
-      type, select_title, base::FilePath(), &info, file_type_index,
-      FILE_PATH_LITERAL(""),
+      type,
+      select_title,
+      base::FilePath(),
+      &info,
+      file_type_index,
+      base::FilePath::StringType(),
       web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow(),
       NULL);
 }
diff --git a/chrome/browser/ui/webui/favicon_source.cc b/chrome/browser/ui/webui/favicon_source.cc
index 6864120..232b6eb 100644
--- a/chrome/browser/ui/webui/favicon_source.cc
+++ b/chrome/browser/ui/webui/favicon_source.cc
@@ -253,10 +253,8 @@ void FaviconSource::OnFaviconDataAvailable(
 
 void FaviconSource::SendDefaultResponse(
     const content::URLDataSource::GotDataCallback& callback) {
-  SendDefaultResponse(IconRequest(callback,
-                                  "",
-                                  16,
-                                  ui::SCALE_FACTOR_100P));
+  SendDefaultResponse(
+      IconRequest(callback, std::string(), 16, ui::SCALE_FACTOR_100P));
 }
 
 void FaviconSource::SendDefaultResponse(const IconRequest& icon_request) {
diff --git a/chrome/browser/ui/webui/feedback_ui.cc b/chrome/browser/ui/webui/feedback_ui.cc
index 3cb20bf..b28e065 100644
--- a/chrome/browser/ui/webui/feedback_ui.cc
+++ b/chrome/browser/ui/webui/feedback_ui.cc
@@ -409,23 +409,23 @@ bool FeedbackHandler::Init() {
       std::string query_str = *it;
       if (StartsWithASCII(query_str, std::string(kSessionIDParameter), true)) {
         ReplaceFirstSubstringAfterOffset(
-            &query_str, 0, kSessionIDParameter, "");
+            &query_str, 0, kSessionIDParameter, std::string());
         if (!base::StringToInt(query_str, &session_id))
           return false;
       } else if (StartsWithASCII(*it, std::string(kTabIndexParameter), true)) {
         ReplaceFirstSubstringAfterOffset(
-            &query_str, 0, kTabIndexParameter, "");
+            &query_str, 0, kTabIndexParameter, std::string());
         if (!base::StringToInt(query_str, &index))
           return false;
       } else if (StartsWithASCII(*it, std::string(kCustomPageUrlParameter),
                                  true)) {
         ReplaceFirstSubstringAfterOffset(
-            &query_str, 0, kCustomPageUrlParameter, "");
+            &query_str, 0, kCustomPageUrlParameter, std::string());
         custom_page_url = query_str;
       } else if (StartsWithASCII(*it, std::string(kCategoryTagParameter),
                                  true)) {
         ReplaceFirstSubstringAfterOffset(
-            &query_str, 0, kCategoryTagParameter, "");
+            &query_str, 0, kCategoryTagParameter, std::string());
         category_tag_ = query_str;
 #if defined(OS_CHROMEOS)
       } else if (StartsWithASCII(*it, std::string(kTimestampParameter), true)) {
diff --git a/chrome/browser/ui/webui/inspect_ui.cc b/chrome/browser/ui/webui/inspect_ui.cc
index b0b67c3..b98ea9e 100644
--- a/chrome/browser/ui/webui/inspect_ui.cc
+++ b/chrome/browser/ui/webui/inspect_ui.cc
@@ -462,7 +462,7 @@ void InspectUI::OnAdbPages(
     targets.Append(target_data);
   }
 
-  std::string json_string = "";
+  std::string json_string;
   base::JSONWriter::Write(&targets, &json_string);
   callback.Run(base::RefCountedString::TakeString(&json_string));
 }
diff --git a/chrome/browser/ui/webui/instant_ui.cc b/chrome/browser/ui/webui/instant_ui.cc
index f84bf9a..23a255c 100644
--- a/chrome/browser/ui/webui/instant_ui.cc
+++ b/chrome/browser/ui/webui/instant_ui.cc
@@ -169,6 +169,7 @@ InstantUI::InstantUI(content::WebUI* web_ui) : WebUIController(web_ui) {
 
 // static
 void InstantUI::RegisterUserPrefs(PrefRegistrySyncable* registry) {
-  registry->RegisterStringPref(prefs::kInstantUIZeroSuggestUrlPrefix, "",
+  registry->RegisterStringPref(prefs::kInstantUIZeroSuggestUrlPrefix,
+                               std::string(),
                                PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
diff --git a/chrome/browser/ui/webui/net_internals/net_internals_ui.cc b/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
index cea9824..0ac1324 100644
--- a/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
+++ b/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
@@ -1409,7 +1409,7 @@ void NetInternalsMessageHandler::IOThreadImpl::OnGetSpdyStatus(
     next_protos_value = Value::CreateStringValue(
         JoinString(net::HttpStreamFactory::next_protos(), ','));
   } else {
-    next_protos_value = Value::CreateStringValue("");
+    next_protos_value = Value::CreateStringValue(std::string());
   }
   status_dict->Set("next_protos", next_protos_value);
 
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.cc b/chrome/browser/ui/webui/options/browser_options_handler.cc
index 48f4f60..54c5c31 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.cc
+++ b/chrome/browser/ui/webui/options/browser_options_handler.cc
@@ -1194,8 +1194,11 @@ void BrowserOptionsHandler::HandleSelectDownloadLocation(
       ui::SelectFileDialog::SELECT_FOLDER,
       l10n_util::GetStringUTF16(IDS_OPTIONS_DOWNLOADLOCATION_BROWSE_TITLE),
       pref_service->GetFilePath(prefs::kDownloadDefaultDirectory),
-      &info, 0, FILE_PATH_LITERAL(""),
-      web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow(), NULL);
+      &info,
+      0,
+      base::FilePath::StringType(),
+      web_ui()->GetWebContents()->GetView()->GetTopLevelNativeWindow(),
+      NULL);
 }
 
 void BrowserOptionsHandler::FileSelected(const base::FilePath& path, int index,
diff --git a/chrome/browser/ui/webui/options/certificate_manager_handler.cc b/chrome/browser/ui/webui/options/certificate_manager_handler.cc
index c1e18da..f30eaec 100644
--- a/chrome/browser/ui/webui/options/certificate_manager_handler.cc
+++ b/chrome/browser/ui/webui/options/certificate_manager_handler.cc
@@ -326,7 +326,7 @@ void CertificateManagerHandler::GetLocalizedValues(
       l10n_util::GetStringUTF16(IDS_CERT_MANAGER_DELETE_CA_DESCRIPTION));
   localized_strings->SetString("unknownCertsTabDeleteConfirm",
       l10n_util::GetStringUTF16(IDS_CERT_MANAGER_DELETE_UNKNOWN_FORMAT));
-  localized_strings->SetString("unknownCertsTabDeleteImpact", "");
+  localized_strings->SetString("unknownCertsTabDeleteImpact", std::string());
 
   // Certificate Restore overlay strings.
   localized_strings->SetString("certificateRestorePasswordDescription",
@@ -614,7 +614,7 @@ void CertificateManagerHandler::ExportPersonalPasswordSelected(
   chrome::UnlockCertSlotIfNecessary(
       selected_cert_list_[0].get(),
       chrome::kCryptoModulePasswordCertExport,
-      "",  // unused.
+      std::string(),  // unused.
       base::Bind(&CertificateManagerHandler::ExportPersonalSlotsUnlocked,
                  base::Unretained(this)));
 }
@@ -723,7 +723,7 @@ void CertificateManagerHandler::ImportPersonalFileRead(
   chrome::UnlockSlotsIfNecessary(
       modules,
       chrome::kCryptoModulePasswordCertImport,
-      "",  // unused.
+      std::string(),  // unused.
       base::Bind(&CertificateManagerHandler::ImportPersonalSlotUnlocked,
                  base::Unretained(this)));
 }
diff --git a/chrome/browser/ui/webui/options/content_settings_handler.cc b/chrome/browser/ui/webui/options/content_settings_handler.cc
index 85249bc..549856b 100644
--- a/chrome/browser/ui/webui/options/content_settings_handler.cc
+++ b/chrome/browser/ui/webui/options/content_settings_handler.cc
@@ -123,7 +123,7 @@ std::string ContentSettingToString(ContentSetting setting) {
       NOTREACHED();
   }
 
-  return "";
+  return std::string();
 }
 
 ContentSetting ContentSettingFromString(const std::string& name) {
@@ -151,8 +151,9 @@ DictionaryValue* GetExceptionForPage(
   DictionaryValue* exception = new DictionaryValue();
   exception->SetString(kOrigin, pattern.ToString());
   exception->SetString(kEmbeddingOrigin,
-      secondary_pattern == ContentSettingsPattern::Wildcard() ? "" :
-          secondary_pattern.ToString());
+                       secondary_pattern == ContentSettingsPattern::Wildcard()
+                           ? std::string()
+                           : secondary_pattern.ToString());
   exception->SetString(kSetting, ContentSettingToString(setting));
   exception->SetString(kSource, provider_name);
   return exception;
@@ -604,7 +605,7 @@ void ContentSettingsHandler::UpdateMediaSettingsView() {
   media_ui_settings.SetString("askText", "mediaStreamAsk");
   media_ui_settings.SetString("blockText", "mediaStreamBlock");
   media_ui_settings.SetBoolean("showBubble", false);
-  media_ui_settings.SetString("bubbleText", "");
+  media_ui_settings.SetString("bubbleText", std::string());
 
   web_ui()->CallJavascriptFunction("ContentSettings.updateMediaUI",
                                    media_ui_settings);
@@ -1052,18 +1053,16 @@ void ContentSettingsHandler::RemoveMediaException(
       mode == "normal" ? GetContentSettingsMap() :
                          GetOTRContentSettingsMap();
   if (settings_map) {
-    settings_map->SetWebsiteSetting(
-        ContentSettingsPattern::FromString(pattern),
-        ContentSettingsPattern::Wildcard(),
-        CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
-        "",
-        NULL);
-    settings_map->SetWebsiteSetting(
-        ContentSettingsPattern::FromString(pattern),
-        ContentSettingsPattern::Wildcard(),
-        CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
-        "",
-        NULL);
+    settings_map->SetWebsiteSetting(ContentSettingsPattern::FromString(pattern),
+                                    ContentSettingsPattern::Wildcard(),
+                                    CONTENT_SETTINGS_TYPE_MEDIASTREAM_MIC,
+                                    std::string(),
+                                    NULL);
+    settings_map->SetWebsiteSetting(ContentSettingsPattern::FromString(pattern),
+                                    ContentSettingsPattern::Wildcard(),
+                                    CONTENT_SETTINGS_TYPE_MEDIASTREAM_CAMERA,
+                                    std::string(),
+                                    NULL);
   }
 }
 
@@ -1088,10 +1087,11 @@ void ContentSettingsHandler::RemoveExceptionFromHostContentSettingsMap(
   if (settings_map) {
     settings_map->SetWebsiteSetting(
         ContentSettingsPattern::FromString(pattern),
-        secondary_pattern.empty() ? ContentSettingsPattern::Wildcard() :
-            ContentSettingsPattern::FromString(secondary_pattern),
+        secondary_pattern.empty()
+            ? ContentSettingsPattern::Wildcard()
+            : ContentSettingsPattern::FromString(secondary_pattern),
         type,
-        "",
+        std::string(),
         NULL);
   }
 }
@@ -1259,7 +1259,7 @@ void ContentSettingsHandler::SetException(const ListValue* args) {
     settings_map->SetContentSetting(ContentSettingsPattern::FromString(pattern),
                                     ContentSettingsPattern::Wildcard(),
                                     type,
-                                    "",
+                                    std::string(),
                                     ContentSettingFromString(setting));
   }
 }
diff --git a/chrome/browser/ui/webui/options/font_settings_handler.cc b/chrome/browser/ui/webui/options/font_settings_handler.cc
index 61f1524..558effc 100644
--- a/chrome/browser/ui/webui/options/font_settings_handler.cc
+++ b/chrome/browser/ui/webui/options/font_settings_handler.cc
@@ -188,8 +188,8 @@ void FontSettingsHandler::FontsListHasLoaded(
       option->Append(new base::StringValue(has_rtl_chars ? "rtl" : "ltr"));
     } else {
       // Add empty name/value to indicate a separator item.
-      option->Append(new base::StringValue(""));
-      option->Append(new base::StringValue(""));
+      option->Append(new base::StringValue(std::string()));
+      option->Append(new base::StringValue(std::string()));
     }
     encoding_list.Append(option);
   }
diff --git a/chrome/browser/ui/webui/options/managed_user_passphrase_handler.cc b/chrome/browser/ui/webui/options/managed_user_passphrase_handler.cc
index 2090137..f3aac91 100644
--- a/chrome/browser/ui/webui/options/managed_user_passphrase_handler.cc
+++ b/chrome/browser/ui/webui/options/managed_user_passphrase_handler.cc
@@ -110,8 +110,8 @@ void ManagedUserPassphraseHandler::IsPassphraseSet(
 void ManagedUserPassphraseHandler::ResetPassphrase(
     const base::ListValue* args) {
   PrefService* pref_service = Profile::FromWebUI(web_ui())->GetPrefs();
-  pref_service->SetString(prefs::kManagedModeLocalPassphrase, "");
-  pref_service->SetString(prefs::kManagedModeLocalSalt, "");
+  pref_service->SetString(prefs::kManagedModeLocalPassphrase, std::string());
+  pref_service->SetString(prefs::kManagedModeLocalSalt, std::string());
 }
 
 void ManagedUserPassphraseHandler::SetLocalPassphrase(
diff --git a/chrome/browser/ui/webui/options/preferences_browsertest.cc b/chrome/browser/ui/webui/options/preferences_browsertest.cc
index 5839538..8dbc971 100644
--- a/chrome/browser/ui/webui/options/preferences_browsertest.cc
+++ b/chrome/browser/ui/webui/options/preferences_browsertest.cc
@@ -343,7 +343,7 @@ void PreferencesBrowserTest::VerifySetPref(const std::string& name,
   std::string observed_json;
   ASSERT_TRUE(content::ExecuteScriptAndExtractString(
       render_view_host_, javascript.str(), &observed_json));
-  VerifyObservedPref(observed_json, name, value, "", false, !commit);
+  VerifyObservedPref(observed_json, name, value, std::string(), false, !commit);
   VerifyAndClearExpectations();
 }
 
@@ -385,7 +385,7 @@ void PreferencesBrowserTest::VerifyCommit(const std::string& name,
 void PreferencesBrowserTest::VerifySetCommit(const std::string& name,
                                              const base::Value* value) {
   ExpectSetCommit(name, value);
-  VerifyCommit(name, value, "");
+  VerifyCommit(name, value, std::string());
   VerifyAndClearExpectations();
 }
 
@@ -476,8 +476,8 @@ IN_PROC_BROWSER_TEST_F(PreferencesBrowserTest, FetchPrefs) {
 
   // Verify notifications when default values are in effect.
   SetupJavaScriptTestEnvironment(pref_names_, &observed_json);
-  VerifyObservedPrefs(observed_json, pref_names_, default_values_,
-                      "", false, false);
+  VerifyObservedPrefs(
+      observed_json, pref_names_, default_values_, std::string(), false, false);
 
   // Verify notifications when recommended values are in effect.
   SetUserPolicies(policy_names_, non_default_values_,
@@ -497,8 +497,12 @@ IN_PROC_BROWSER_TEST_F(PreferencesBrowserTest, FetchPrefs) {
   ClearUserPolicies();
   SetUserValues(pref_names_, non_default_values_);
   SetupJavaScriptTestEnvironment(pref_names_, &observed_json);
-  VerifyObservedPrefs(observed_json, pref_names_, non_default_values_,
-                      "", false, false);
+  VerifyObservedPrefs(observed_json,
+                      pref_names_,
+                      non_default_values_,
+                      std::string(),
+                      false,
+                      false);
 }
 
 // Verifies that setting a user-modified pref value through the JavaScript
@@ -550,7 +554,7 @@ IN_PROC_BROWSER_TEST_F(PreferencesBrowserTest, DialogPrefsSetRollback) {
   ASSERT_NO_FATAL_FAILURE(SetupJavaScriptTestEnvironment(pref_names_, NULL));
   for (size_t i = 0; i < pref_names_.size(); ++i) {
     VerifySetPref(pref_names_[i], types_[i], non_default_values_[i], false);
-    VerifyRollback(pref_names_[i], default_values_[i], "");
+    VerifyRollback(pref_names_[i], default_values_[i], std::string());
   }
 
   // Verify behavior when recommended values are in effect.
@@ -592,7 +596,7 @@ IN_PROC_BROWSER_TEST_F(PreferencesBrowserTest, DialogPrefsClearRollback) {
   ASSERT_NO_FATAL_FAILURE(SetupJavaScriptTestEnvironment(pref_names_, NULL));
   for (size_t i = 0; i < pref_names_.size(); ++i) {
     VerifyClearPref(pref_names_[i], default_values_[i], false);
-    VerifyRollback(pref_names_[i], non_default_values_[i], "");
+    VerifyRollback(pref_names_[i], non_default_values_[i], std::string());
   }
 }
 
@@ -624,15 +628,19 @@ IN_PROC_BROWSER_TEST_F(PreferencesBrowserTest, NotificationsOnBackendChanges) {
   StartObserving();
   ClearUserPolicies();
   FinishObserving(&observed_json);
-  VerifyObservedPrefs(observed_json, pref_names_, default_values_,
-                      "", false, false);
+  VerifyObservedPrefs(
+      observed_json, pref_names_, default_values_, std::string(), false, false);
 
   // Verify notifications when user-modified values come into effect.
   StartObserving();
   SetUserValues(pref_names_, non_default_values_);
   FinishObserving(&observed_json);
-  VerifyObservedPrefs(observed_json, pref_names_, non_default_values_,
-                      "", false, false);
+  VerifyObservedPrefs(observed_json,
+                      pref_names_,
+                      non_default_values_,
+                      std::string(),
+                      false,
+                      false);
 }
 
 #if defined(OS_CHROMEOS)
diff --git a/chrome/browser/ui/webui/policy_ui_browsertest.cc b/chrome/browser/ui/webui/policy_ui_browsertest.cc
index 6af1613..6293fef 100644
--- a/chrome/browser/ui/webui/policy_ui_browsertest.cc
+++ b/chrome/browser/ui/webui/policy_ui_browsertest.cc
@@ -43,7 +43,7 @@ std::vector<std::string> PopulateExpectedPolicy(
         metadata->scope == policy::POLICY_SCOPE_MACHINE ?
             IDS_POLICY_SCOPE_DEVICE : IDS_POLICY_SCOPE_USER));
   } else {
-    expected_policy.push_back("");
+    expected_policy.push_back(std::string());
   }
 
   // Populate expected level.
@@ -52,7 +52,7 @@ std::vector<std::string> PopulateExpectedPolicy(
         metadata->level == policy::POLICY_LEVEL_RECOMMENDED ?
             IDS_POLICY_LEVEL_RECOMMENDED : IDS_POLICY_LEVEL_MANDATORY));
   } else {
-    expected_policy.push_back("");
+    expected_policy.push_back(std::string());
   }
 
   // Populate expected policy name.
@@ -178,7 +178,7 @@ IN_PROC_BROWSER_TEST_F(PolicyUITest, SendPolicyNames) {
   for (const policy::PolicyDefinitionList::Entry* policy = policies->begin;
       policy != policies->end; ++policy) {
     expected_policies.push_back(
-        PopulateExpectedPolicy(policy->name, "", NULL, false));
+        PopulateExpectedPolicy(policy->name, std::string(), NULL, false));
   }
 
   // Retrieve the contents of the policy table from the UI and verify that it
@@ -240,7 +240,8 @@ IN_PROC_BROWSER_TEST_F(PolicyUITest, SendPolicyValues) {
        policy != policies->end; ++policy) {
     std::map<std::string, std::string>::const_iterator it =
         expected_values.find(policy->name);
-    const std::string value = it == expected_values.end() ? "" : it->second;
+    const std::string value =
+        it == expected_values.end() ? std::string() : it->second;
     const policy::PolicyMap::Entry* metadata = values.Get(policy->name);
     expected_policies.insert(
         metadata ? expected_policies.begin() + first_unset_position++ :
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
index 0525da3..7899260 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_handler.cc
@@ -866,7 +866,7 @@ void PrintPreviewHandler::SelectFile(const base::FilePath& default_filename) {
       sticky_settings->save_path()->Append(default_filename),
       &file_type_info,
       0,
-      FILE_PATH_LITERAL(""),
+      base::FilePath::StringType(),
       platform_util::GetTopLevel(
           preview_web_contents()->GetView()->GetNativeView()),
       NULL);
diff --git a/chrome/browser/ui/webui/print_preview/print_preview_ui.cc b/chrome/browser/ui/webui/print_preview/print_preview_ui.cc
index 52cbe91..4e10802 100644
--- a/chrome/browser/ui/webui/print_preview/print_preview_ui.cc
+++ b/chrome/browser/ui/webui/print_preview/print_preview_ui.cc
@@ -571,7 +571,7 @@ void PrintPreviewUI::OnClosePrintPreviewDialog() {
   ConstrainedWebDialogDelegate* delegate = GetConstrainedDelegate();
   if (!delegate)
     return;
-  delegate->GetWebDialogDelegate()->OnDialogClosed("");
+  delegate->GetWebDialogDelegate()->OnDialogClosed(std::string());
   delegate->OnDialogCloseFromWebUI();
 }
 
diff --git a/chrome/browser/ui/webui/signin/profile_signin_confirmation_dialog_unittest.cc b/chrome/browser/ui/webui/signin/profile_signin_confirmation_dialog_unittest.cc
index e24b730..cd6f5fe 100644
--- a/chrome/browser/ui/webui/signin/profile_signin_confirmation_dialog_unittest.cc
+++ b/chrome/browser/ui/webui/signin/profile_signin_confirmation_dialog_unittest.cc
@@ -142,11 +142,11 @@ class ProfileSigninConfirmationDialogTest : public testing::Test {
                                    false);
 
     // Create a dialog, but don't display it.
-    dialog_ = new ProfileSigninConfirmationDialog(
-        profile_.get(), "",
-        base::Bind(&base::DoNothing),
-        base::Bind(&base::DoNothing),
-        base::Bind(&base::DoNothing));
+    dialog_ = new ProfileSigninConfirmationDialog(profile_.get(),
+                                                  std::string(),
+                                                  base::Bind(&base::DoNothing),
+                                                  base::Bind(&base::DoNothing),
+                                                  base::Bind(&base::DoNothing));
   }
 
   virtual void TearDown() OVERRIDE {
@@ -204,10 +204,10 @@ TEST_F(ProfileSigninConfirmationDialogTest, PromptForNewProfile_Extensions) {
               &ProfileSigninConfirmationDialog::CheckShouldPromptForNewProfile,
               base::Unretained(dialog_))));
 
-  scoped_refptr<extensions::Extension> extension = CreateExtension("foo", "");
+  scoped_refptr<extensions::Extension> extension =
+      CreateExtension("foo", std::string());
   extensions->extension_prefs()->AddGrantedPermissions(
-      extension->id(),
-      make_scoped_refptr(new extensions::PermissionSet));
+      extension->id(), make_scoped_refptr(new extensions::PermissionSet));
   extensions->AddExtension(extension);
   EXPECT_TRUE(
       GetCallbackResult(
diff --git a/chrome/browser/ui/webui/sync_setup_handler_unittest.cc b/chrome/browser/ui/webui/sync_setup_handler_unittest.cc
index f958519..19f2d0e 100644
--- a/chrome/browser/ui/webui/sync_setup_handler_unittest.cc
+++ b/chrome/browser/ui/webui/sync_setup_handler_unittest.cc
@@ -457,8 +457,13 @@ TEST_P(SyncSetupHandlerTest, DisplayBasicLogin) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", false, GoogleServiceAuthError::NONE, "", true, "");
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           false,
+                           GoogleServiceAuthError::NONE,
+                           std::string(),
+                           true,
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -494,8 +499,13 @@ TEST_P(SyncSetupHandlerTest, DisplayForceLogin) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", false, GoogleServiceAuthError::NONE, "", true, "");
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           false,
+                           GoogleServiceAuthError::NONE,
+                           std::string(),
+                           true,
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -679,7 +689,7 @@ TEST_P(SyncSetupHandlerTest, HandleGaiaAuthFailure) {
 
   if (!SyncPromoUI::UseWebBasedSigninFlow()) {
     // Fake a failed signin attempt.
-    handler_->TryLogin(kTestUser, kTestPassword, "", "");
+    handler_->TryLogin(kTestUser, kTestPassword, std::string(), std::string());
     GoogleServiceAuthError error(
         GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS);
     handler_->SigninFailed(error);
@@ -695,9 +705,13 @@ TEST_P(SyncSetupHandlerTest, HandleGaiaAuthFailure) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", false, GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS,
-        kTestUser, true, "");
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           false,
+                           GoogleServiceAuthError::INVALID_GAIA_CREDENTIALS,
+                           kTestUser,
+                           true,
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -718,7 +732,7 @@ TEST_P(SyncSetupHandlerTest, HandleCaptcha) {
 
   if (!SyncPromoUI::UseWebBasedSigninFlow()) {
     // Fake a failed signin attempt that requires a captcha.
-    handler_->TryLogin(kTestUser, kTestPassword, "", "");
+    handler_->TryLogin(kTestUser, kTestPassword, std::string(), std::string());
     GoogleServiceAuthError error =
         GoogleServiceAuthError::FromClientLoginCaptchaChallenge(
             "token", GURL(kTestCaptchaImageUrl), GURL(kTestCaptchaUnlockUrl));
@@ -734,9 +748,13 @@ TEST_P(SyncSetupHandlerTest, HandleCaptcha) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", false, GoogleServiceAuthError::CAPTCHA_REQUIRED,
-        kTestUser, true, kTestCaptchaImageUrl);
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           false,
+                           GoogleServiceAuthError::CAPTCHA_REQUIRED,
+                           kTestUser,
+                           true,
+                           kTestCaptchaImageUrl);
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -758,7 +776,7 @@ TEST_P(SyncSetupHandlerTest, UnrecoverableErrorInitializingSync) {
     ASSERT_EQ(1U, web_ui_.call_data().size());
     // Fake a successful GAIA request (gaia credentials valid, but signin not
     // complete yet).
-    handler_->TryLogin(kTestUser, kTestPassword, "", "");
+    handler_->TryLogin(kTestUser, kTestPassword, std::string(), std::string());
     handler_->GaiaCredentialsValid();
     ASSERT_EQ(2U, web_ui_.call_data().size());
     EXPECT_EQ("SyncSetupOverlay.showSuccessAndSettingUp",
@@ -780,9 +798,13 @@ TEST_P(SyncSetupHandlerTest, UnrecoverableErrorInitializingSync) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", true, GoogleServiceAuthError::NONE,
-        kTestUser, true, "");
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           true,
+                           GoogleServiceAuthError::NONE,
+                           kTestUser,
+                           true,
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -803,7 +825,7 @@ TEST_P(SyncSetupHandlerTest, GaiaErrorInitializingSync) {
     ASSERT_EQ(1U, web_ui_.call_data().size());
     // Fake a successful GAIA request (gaia credentials valid, but signin not
     // complete yet).
-    handler_->TryLogin(kTestUser, kTestPassword, "", "");
+    handler_->TryLogin(kTestUser, kTestPassword, std::string(), std::string());
     handler_->GaiaCredentialsValid();
     ASSERT_EQ(2U, web_ui_.call_data().size());
     EXPECT_EQ("SyncSetupOverlay.showSuccessAndSettingUp",
@@ -826,9 +848,13 @@ TEST_P(SyncSetupHandlerTest, GaiaErrorInitializingSync) {
     // Now make sure that the appropriate params are being passed.
     DictionaryValue* dictionary;
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
-    CheckShowSyncSetupArgs(
-        dictionary, "", false, GoogleServiceAuthError::SERVICE_UNAVAILABLE,
-        kTestUser, true, "");
+    CheckShowSyncSetupArgs(dictionary,
+                           std::string(),
+                           false,
+                           GoogleServiceAuthError::SERVICE_UNAVAILABLE,
+                           kTestUser,
+                           true,
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -837,7 +863,7 @@ TEST_P(SyncSetupHandlerTest, GaiaErrorInitializingSync) {
 
 TEST_P(SyncSetupHandlerTest, TestSyncEverything) {
   std::string args = GetConfiguration(
-      NULL, SYNC_ALL_DATA, GetAllTypes(), "", ENCRYPT_PASSWORDS);
+      NULL, SYNC_ALL_DATA, GetAllTypes(), std::string(), ENCRYPT_PASSWORDS);
   ListValue list_args;
   list_args.Append(new StringValue(args));
   EXPECT_CALL(*mock_pss_, IsPassphraseRequiredForDecryption())
@@ -855,7 +881,7 @@ TEST_P(SyncSetupHandlerTest, TestSyncEverything) {
 
 TEST_P(SyncSetupHandlerTest, TurnOnEncryptAll) {
   std::string args = GetConfiguration(
-      NULL, SYNC_ALL_DATA, GetAllTypes(), "", ENCRYPT_ALL_DATA);
+      NULL, SYNC_ALL_DATA, GetAllTypes(), std::string(), ENCRYPT_ALL_DATA);
   ListValue list_args;
   list_args.Append(new StringValue(args));
   EXPECT_CALL(*mock_pss_, IsPassphraseRequiredForDecryption())
@@ -874,7 +900,7 @@ TEST_P(SyncSetupHandlerTest, TurnOnEncryptAll) {
 
 TEST_P(SyncSetupHandlerTest, TestPassphraseStillRequired) {
   std::string args = GetConfiguration(
-      NULL, SYNC_ALL_DATA, GetAllTypes(), "", ENCRYPT_PASSWORDS);
+      NULL, SYNC_ALL_DATA, GetAllTypes(), std::string(), ENCRYPT_PASSWORDS);
   ListValue list_args;
   list_args.Append(new StringValue(args));
   EXPECT_CALL(*mock_pss_, IsPassphraseRequiredForDecryption())
@@ -990,8 +1016,11 @@ TEST_P(SyncSetupHandlerTest, TestSyncIndividualTypes) {
   for (it = user_selectable_types.First(); it.Good(); it.Inc()) {
     syncer::ModelTypeSet type_to_set;
     type_to_set.Put(it.Get());
-    std::string args = GetConfiguration(
-        NULL, CHOOSE_WHAT_TO_SYNC, type_to_set, "", ENCRYPT_PASSWORDS);
+    std::string args = GetConfiguration(NULL,
+                                        CHOOSE_WHAT_TO_SYNC,
+                                        type_to_set,
+                                        std::string(),
+                                        ENCRYPT_PASSWORDS);
     ListValue list_args;
     list_args.Append(new StringValue(args));
     EXPECT_CALL(*mock_pss_, IsPassphraseRequiredForDecryption())
@@ -1010,8 +1039,11 @@ TEST_P(SyncSetupHandlerTest, TestSyncIndividualTypes) {
 }
 
 TEST_P(SyncSetupHandlerTest, TestSyncAllManually) {
-  std::string args = GetConfiguration(
-      NULL, CHOOSE_WHAT_TO_SYNC, GetAllTypes(), "", ENCRYPT_PASSWORDS);
+  std::string args = GetConfiguration(NULL,
+                                      CHOOSE_WHAT_TO_SYNC,
+                                      GetAllTypes(),
+                                      std::string(),
+                                      ENCRYPT_PASSWORDS);
   ListValue list_args;
   list_args.Append(new StringValue(args));
   EXPECT_CALL(*mock_pss_, IsPassphraseRequiredForDecryption())
@@ -1074,12 +1106,12 @@ TEST_P(SyncSetupHandlerTest, ShowSyncSetupWithAuthError) {
     ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
     // We should display a login screen with a non-editable username filled in.
     CheckShowSyncSetupArgs(dictionary,
-                           "",
+                           std::string(),
                            false,
                            GoogleServiceAuthError::NONE,
                            kTestUser,
                            false,
-                           "");
+                           std::string());
   } else {
     ASSERT_FALSE(handler_->is_configuring_sync());
     ASSERT_TRUE(handler_->have_signin_tracker());
@@ -1244,9 +1276,9 @@ TEST_P(SyncSetupHandlerTest, SubmitAuthWithInvalidUsername) {
   DictionaryValue args;
   args.SetString("user", "user@not_allowed.com");
   args.SetString("pass", "password");
-  args.SetString("captcha", "");
-  args.SetString("otp", "");
-  args.SetString("accessCode", "");
+  args.SetString("captcha", std::string());
+  args.SetString("otp", std::string());
+  args.SetString("accessCode", std::string());
   std::string json;
   base::JSONWriter::Write(&args, &json);
   ListValue list_args;
@@ -1267,8 +1299,13 @@ TEST_P(SyncSetupHandlerTest, SubmitAuthWithInvalidUsername) {
   DictionaryValue* dictionary;
   ASSERT_TRUE(data.arg2->GetAsDictionary(&dictionary));
   std::string err = l10n_util::GetStringUTF8(IDS_SYNC_LOGIN_NAME_PROHIBITED);
-  CheckShowSyncSetupArgs(
-      dictionary, err, false, GoogleServiceAuthError::NONE, "", true, "");
+  CheckShowSyncSetupArgs(dictionary,
+                         err,
+                         false,
+                         GoogleServiceAuthError::NONE,
+                         std::string(),
+                         true,
+                         std::string());
   handler_->CloseSyncSetup();
   EXPECT_EQ(NULL,
             LoginUIServiceFactory::GetForProfile(
diff --git a/chrome/browser/ui/webui/version_ui.cc b/chrome/browser/ui/webui/version_ui.cc
index 678492a..6497ae0 100644
--- a/chrome/browser/ui/webui/version_ui.cc
+++ b/chrome/browser/ui/webui/version_ui.cc
@@ -92,7 +92,7 @@ content::WebUIDataSource* CreateVersionUIDataSource(Profile* profile) {
   html_source->AddString("command_line",
       WideToUTF16(CommandLine::ForCurrentProcess()->GetCommandLineString()));
 #elif defined(OS_POSIX)
-  std::string command_line = "";
+  std::string command_line;
   typedef std::vector<std::string> ArgvList;
   const ArgvList& argv = CommandLine::ForCurrentProcess()->argv();
   for (ArgvList::const_iterator iter = argv.begin(); iter != argv.end(); iter++)