Loads local resources from current locale subtree if available, if not it falls back to extension subtree.

We look for ext_root/foo/bar.js under ext_root/_locales/fr/foo/bar.js if current locale is fr. If there is no fr specific resource we load ext_root/foo/bar.js instead.

Lots of small refactoring to replace FilePath with ExtensionResource.


BUG=12131
TEST=See unittest for sample tree.


Review URL: http://codereview.chromium.org/256022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@28333 0039d316-1c4b-4281-b951-d872f2087c98

31 files changed, 420 insertions, 168 deletions

diff --git a/chrome/browser/extensions/crx_installer.cc b/chrome/browser/extensions/crx_installer.cc
index c90870f..ac7ea52 100644
--- a/chrome/browser/extensions/crx_installer.cc
+++ b/chrome/browser/extensions/crx_installer.cc
@@ -124,8 +124,9 @@ void CrxInstaller::OnUnpackSuccess(const FilePath& temp_dir,
   }
 
   if (client_.get()) {
-    DecodeInstallIcon(extension_->GetIconPath(Extension::EXTENSION_ICON_LARGE),
-                      &install_icon_);
+    FilePath icon_path =
+        extension_->GetIconPath(Extension::EXTENSION_ICON_LARGE).GetFilePath();
+    DecodeInstallIcon(icon_path, &install_icon_);
   }
   ui_loop_->PostTask(FROM_HERE, NewRunnableMethod(this,
       &CrxInstaller::ConfirmInstall));
diff --git a/chrome/browser/extensions/execute_code_in_tab_function.cc b/chrome/browser/extensions/execute_code_in_tab_function.cc
index bcca094..92d6fb9 100755
--- a/chrome/browser/extensions/execute_code_in_tab_function.cc
+++ b/chrome/browser/extensions/execute_code_in_tab_function.cc
@@ -7,7 +7,7 @@
 #include "chrome/browser/browser.h"
 #include "chrome/browser/extensions/extension_tabs_module.h"
 #include "chrome/browser/extensions/extension_tabs_module_constants.h"
-#include "chrome/browser/net/file_reader.h"
+#include "chrome/browser/extensions/file_reader.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_error_utils.h"
@@ -80,15 +80,15 @@ bool ExecuteCodeInTabFunction::RunImpl() {
   if (script_info->HasKey(kFileKey)) {
     if (!script_info->GetString(kFileKey, &relative_path))
       return false;
-    file_path_ = GetExtension()->GetResourcePath(relative_path);
+    resource_ = GetExtension()->GetResource(relative_path);
   }
-  if (file_path_.empty()) {
+  if (resource_.extension_root().empty() || resource_.relative_path().empty()) {
     error_ = keys::kNoCodeOrFileToExecuteError;
     return false;
   }
 
   scoped_refptr<FileReader> file_reader(new FileReader(
-      file_path_, NewCallback(this, &ExecuteCodeInTabFunction::DidLoadFile)));
+      resource_, NewCallback(this, &ExecuteCodeInTabFunction::DidLoadFile)));
   file_reader->Start();
   AddRef();  // Keep us alive until DidLoadFile is called.
 
@@ -102,10 +102,10 @@ void ExecuteCodeInTabFunction::DidLoadFile(bool success,
   } else {
 #if defined(OS_POSIX)
     error_ = ExtensionErrorUtils::FormatErrorMessage(keys::kLoadFileError,
-        file_path_.value());
+        resource_.relative_path().value());
 #elif defined(OS_WIN)
     error_ = ExtensionErrorUtils::FormatErrorMessage(keys::kLoadFileError,
-        WideToUTF8(file_path_.value()));
+        WideToUTF8(resource_.relative_path().value()));
 #endif  // OS_WIN
     SendResponse(false);
   }
diff --git a/chrome/browser/extensions/execute_code_in_tab_function.h b/chrome/browser/extensions/execute_code_in_tab_function.h
index e887e7c..5ea91e6 100755
--- a/chrome/browser/extensions/execute_code_in_tab_function.h
+++ b/chrome/browser/extensions/execute_code_in_tab_function.h
@@ -10,6 +10,7 @@
 
 #include "base/file_path.h"
 #include "chrome/browser/extensions/extension_function.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/notification_service.h"
 #include "chrome/common/notification_registrar.h"
 
@@ -40,8 +41,9 @@ class ExecuteCodeInTabFunction : public AsyncExtensionFunction,
   // Id of tab which executes code.
   int execute_tab_id_;
 
-  // Contain path of file which is specified in JSON arguments.
-  FilePath file_path_;
+  // Contains extension resource built from path of file which is
+  // specified in JSON arguments.
+  ExtensionResource resource_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXECUTE_CODE_IN_TAB_FUNCTION_H__
diff --git a/chrome/browser/extensions/extension_disabled_infobar_delegate.cc b/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
index e3b0ca8..14cc3e7 100644
--- a/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
+++ b/chrome/browser/extensions/extension_disabled_infobar_delegate.cc
@@ -7,11 +7,13 @@
 #include "app/l10n_util.h"
 #include "chrome/browser/chrome_thread.h"
 #include "chrome/browser/extensions/crx_installer.h"
+#include "chrome/browser/extensions/extension_file_util.h"
 #include "chrome/browser/extensions/extension_install_ui.h"
 #include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/tab_contents/infobar_delegate.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/browser/browser_list.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/notification_registrar.h"
 #include "chrome/common/notification_service.h"
 #include "grit/generated_resources.h"
@@ -28,7 +30,7 @@ class ExtensionDisabledDialogDelegate
     AddRef();  // balanced in ContinueInstall or AbortInstall.
 
     // Do this now because we can't touch extension on the file loop.
-    install_icon_path_ =
+    install_icon_resource_ =
         extension_->GetIconPath(Extension::EXTENSION_ICON_LARGE);
 
     ChromeThread::GetMessageLoop(ChromeThread::FILE)->PostTask(FROM_HERE,
@@ -48,7 +50,8 @@ class ExtensionDisabledDialogDelegate
  private:
   void Start() {
     // We start on the file thread so we can decode the install icon.
-    CrxInstaller::DecodeInstallIcon(install_icon_path_, &install_icon_);
+    FilePath install_icon_path = install_icon_resource_.GetFilePath();
+    CrxInstaller::DecodeInstallIcon(install_icon_path, &install_icon_);
     // Then we display the UI on the UI thread.
     ui_loop_->PostTask(FROM_HERE,
         NewRunnableMethod(this,
@@ -64,7 +67,7 @@ class ExtensionDisabledDialogDelegate
   Profile* profile_;
   ExtensionsService* service_;
   Extension* extension_;
-  FilePath install_icon_path_;
+  ExtensionResource install_icon_resource_;
   scoped_ptr<SkBitmap> install_icon_;
   MessageLoop* ui_loop_;
 };
diff --git a/chrome/browser/extensions/extension_file_util.cc b/chrome/browser/extensions/extension_file_util.cc
index 28a7482..32c4819 100644
--- a/chrome/browser/extensions/extension_file_util.cc
+++ b/chrome/browser/extensions/extension_file_util.cc
@@ -137,7 +137,7 @@ bool ValidateExtension(Extension* extension, std::string* error) {
   // Validate icons exist.
   for (std::map<int, std::string>::const_iterator iter =
        extension->icons().begin(); iter != extension->icons().end(); ++iter) {
-    if (!file_util::PathExists(extension->GetResourcePath(iter->second))) {
+    if (extension->GetResource(iter->second).GetFilePath().empty()) {
       *error = StringPrintf("Could not load extension icon '%s'.",
                             iter->second.c_str());
       return false;
@@ -172,8 +172,9 @@ bool ValidateExtension(Extension* extension, std::string* error) {
     const UserScript& script = extension->content_scripts()[i];
 
     for (size_t j = 0; j < script.js_scripts().size(); j++) {
-      const FilePath& path = script.js_scripts()[j].path();
-      if (!file_util::PathExists(path)) {
+      const FilePath& path =
+        script.js_scripts()[j].resource().GetFilePath();
+      if (path.empty()) {
         *error = StringPrintf("Could not load '%s' for content script.",
                               WideToUTF8(path.ToWStringHack()).c_str());
         return false;
@@ -181,8 +182,9 @@ bool ValidateExtension(Extension* extension, std::string* error) {
     }
 
     for (size_t j = 0; j < script.css_scripts().size(); j++) {
-      const FilePath& path = script.css_scripts()[j].path();
-      if (!file_util::PathExists(path)) {
+      const FilePath& path =
+        script.css_scripts()[j].resource().GetFilePath();
+      if (path.empty()) {
         *error = StringPrintf("Could not load '%s' for content script.",
                               WideToUTF8(path.ToWStringHack()).c_str());
         return false;
@@ -219,7 +221,7 @@ bool ValidateExtension(Extension* extension, std::string* error) {
     const std::vector<std::string>& icon_paths = page_action->icon_paths();
     for (std::vector<std::string>::const_iterator iter = icon_paths.begin();
          iter != icon_paths.end(); ++iter) {
-      if (!file_util::PathExists(extension->GetResourcePath(*iter))) {
+      if (extension->GetResource(*iter).GetFilePath().empty()) {
         *error = StringPrintf("Could not load icon '%s' for page action.",
                               iter->c_str());
         return false;
@@ -233,7 +235,7 @@ bool ValidateExtension(Extension* extension, std::string* error) {
     const std::vector<std::string>& icon_paths = browser_action->icon_paths();
     for (std::vector<std::string>::const_iterator iter = icon_paths.begin();
          iter != icon_paths.end(); ++iter) {
-      if (!file_util::PathExists(extension->GetResourcePath(*iter))) {
+      if (extension->GetResource(*iter).GetFilePath().empty()) {
         *error = StringPrintf("Could not load icon '%s' for browser action.",
                               iter->c_str());
         return false;
diff --git a/chrome/browser/extensions/extension_l10n_util.cc b/chrome/browser/extensions/extension_l10n_util.cc
index 2c66ff9..411de59 100644
--- a/chrome/browser/extensions/extension_l10n_util.cc
+++ b/chrome/browser/extensions/extension_l10n_util.cc
@@ -144,4 +144,16 @@ ExtensionMessageBundle* LoadMessageCatalogs(
                                         error);
 }
 
+FilePath GetL10nRelativePath(const FilePath& relative_resource_path) {
+  // Get locale relative path.
+  static std::string current_locale = l10n_util::GetApplicationLocale(L"");
+  std::replace(current_locale.begin(), current_locale.end(), '-', '_');
+
+  FilePath locale_relative_path;
+  return locale_relative_path
+      .AppendASCII(Extension::kLocaleFolder)
+      .AppendASCII(current_locale)
+      .Append(relative_resource_path);
+}
+
 }  // namespace extension_l10n_util
diff --git a/chrome/browser/extensions/extension_l10n_util.h b/chrome/browser/extensions/extension_l10n_util.h
index 98759ab..b3be601 100644
--- a/chrome/browser/extensions/extension_l10n_util.h
+++ b/chrome/browser/extensions/extension_l10n_util.h
@@ -55,6 +55,9 @@ ExtensionMessageBundle* LoadMessageCatalogs(const FilePath& locale_path,
                                             const std::string& app_locale,
                                             std::string* error);
 
+// Returns relative l10n path to the resource.
+FilePath GetL10nRelativePath(const FilePath& relative_resource_path);
+
 }  // namespace extension_l10n_util
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_L10N_UTIL_H_
diff --git a/chrome/browser/extensions/extension_l10n_util_unittest.cc b/chrome/browser/extensions/extension_l10n_util_unittest.cc
index f674f69..5c0df39 100644
--- a/chrome/browser/extensions/extension_l10n_util_unittest.cc
+++ b/chrome/browser/extensions/extension_l10n_util_unittest.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/extensions/extension_l10n_util.h"
 
+#include "app/l10n_util.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
@@ -143,4 +144,34 @@ TEST(ExtensionL10nUtil, LoadMessageCatalogsDuplicateKeys) {
   EXPECT_TRUE(error.empty());
 }
 
+bool PathsAreEqual(const FilePath& path1, const FilePath& path2) {
+  FilePath::StringType path1_str = path1.value();
+  std::replace(path1_str.begin(), path1_str.end(), '\\', '/');
+
+  FilePath::StringType path2_str = path2.value();
+  std::replace(path2_str.begin(), path2_str.end(), '\\', '/');
+
+  if (path1_str == path2_str) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+TEST(ExtensionL10nUtil, GetL10nRelativePath) {
+  static std::string current_locale = l10n_util::GetApplicationLocale(L"");
+  std::replace(current_locale.begin(), current_locale.end(), '-', '_');
+
+  FilePath locale_path;
+  locale_path = locale_path
+      .AppendASCII(Extension::kLocaleFolder)
+      .AppendASCII(current_locale)
+      .AppendASCII("foo")
+      .AppendASCII("bar.js");
+
+  FilePath result = extension_l10n_util::GetL10nRelativePath(
+      FilePath(FILE_PATH_LITERAL("foo/bar.js")));
+  EXPECT_TRUE(PathsAreEqual(locale_path, result));
+}
+
 }  // namespace
diff --git a/chrome/browser/extensions/extension_protocols.cc b/chrome/browser/extensions/extension_protocols.cc
index 3ff9c51..3be8337 100644
--- a/chrome/browser/extensions/extension_protocols.cc
+++ b/chrome/browser/extensions/extension_protocols.cc
@@ -7,6 +7,7 @@
 #include "base/string_util.h"
 #include "chrome/browser/net/chrome_url_request_context.h"
 #include "chrome/common/extensions/extension.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/url_constants.h"
 #include "googleurl/src/url_util.h"
 #include "net/base/net_util.h"
@@ -26,10 +27,10 @@ static URLRequestJob* CreateExtensionURLRequestJob(URLRequest* request,
     return NULL;
   }
 
-  std::string resource = request->url().path();
-  FilePath path = Extension::GetResourcePath(directory_path, resource);
+  ExtensionResource resource =
+    Extension::GetResource(directory_path, request->url().path());
 
-  return new URLRequestFileJob(request, path);
+  return new URLRequestFileJob(request, resource.GetFilePath());
 }
 
 // Factory registered with URLRequest to create URLRequestJobs for
@@ -41,10 +42,11 @@ static URLRequestJob* CreateUserScriptURLRequestJob(URLRequest* request,
 
   // chrome-user-script:/user-script-name.user.js
   FilePath directory_path = context->user_script_dir_path();
-  std::string resource = request->url().path();
 
-  FilePath path = Extension::GetResourcePath(directory_path, resource);
-  return new URLRequestFileJob(request, path);
+  ExtensionResource resource =
+    Extension::GetResource(directory_path, request->url().path());
+
+  return new URLRequestFileJob(request, resource.GetFilePath());
 }
 
 void RegisterExtensionProtocols() {
diff --git a/chrome/browser/extensions/extensions_service_unittest.cc b/chrome/browser/extensions/extensions_service_unittest.cc
index fa257e0..578bde2 100644
--- a/chrome/browser/extensions/extensions_service_unittest.cc
+++ b/chrome/browser/extensions/extensions_service_unittest.cc
@@ -540,21 +540,15 @@ TEST_F(ExtensionsServiceTest, LoadAllExtensionsFromDirectorySuccess) {
   EXPECT_EQ("https://*.google.com/*",
             scripts[0].url_patterns()[2].GetAsString());
   EXPECT_EQ(2u, scripts[0].js_scripts().size());
-  EXPECT_EQ(
-      NormalizeSeperators(extension->path().AppendASCII("script1.js").value()),
-      NormalizeSeperators(scripts[0].js_scripts()[0].path().value()));
-  EXPECT_EQ(
-      NormalizeSeperators(extension->path().AppendASCII("script2.js").value()),
-      NormalizeSeperators(scripts[0].js_scripts()[1].path().value()));
+  EXPECT_TRUE(scripts[0].js_scripts()[0].resource().ComparePathWithDefault(
+      extension->path().AppendASCII("script1.js")));
+  EXPECT_TRUE(scripts[0].js_scripts()[1].resource().ComparePathWithDefault(
+      extension->path().AppendASCII("script2.js")));
   EXPECT_TRUE(extension->plugins().empty());
   EXPECT_EQ(1u, scripts[1].url_patterns().size());
   EXPECT_EQ("http://*.news.com/*", scripts[1].url_patterns()[0].GetAsString());
-  EXPECT_EQ(
-      NormalizeSeperators(extension->path()
-                          .AppendASCII("js_files")
-                          .AppendASCII("script3.js")
-                          .value()),
-      NormalizeSeperators(scripts[1].js_scripts()[0].path().value()));
+  EXPECT_TRUE(scripts[1].js_scripts()[0].resource().ComparePathWithDefault(
+      extension->path().AppendASCII("js_files").AppendASCII("script3.js")));
   const std::vector<URLPattern> permissions = extension->host_permissions();
   ASSERT_EQ(2u, permissions.size());
   EXPECT_EQ("http://*.google.com/*", permissions[0].GetAsString());
diff --git a/chrome/browser/extensions/extensions_ui.cc b/chrome/browser/extensions/extensions_ui.cc
index db10a9a..7313f50 100644
--- a/chrome/browser/extensions/extensions_ui.cc
+++ b/chrome/browser/extensions/extensions_ui.cc
@@ -239,15 +239,11 @@ static void CreateScriptFileDetailValue(
 
   ListValue *list = new ListValue();
   for (size_t i = 0; i < scripts.size(); ++i) {
-    const UserScript::File &file = scripts[i];
-    // We are passing through GURLs to canonicalize the output to a valid
-    // URL path fragment.
-    GURL script_url = net::FilePathToFileURL(file.path());
-    GURL extension_url = net::FilePathToFileURL(extension_path);
-    std::string relative_path =
-        script_url.spec().substr(extension_url.spec().length() + 1);
-
-    list->Append(new StringValue(relative_path));
+    const UserScript::File& file = scripts[i];
+    // TODO(cira): this information is not used on extension page yet. We
+    // may want to display actual resource that got loaded, not default.
+    list->Append(
+        new StringValue(file.resource().relative_path().value()));
   }
   script_data->Set(key, list);
 }
@@ -292,8 +288,8 @@ DictionaryValue* ExtensionsDOMHandler::CreateExtensionDetailValue(
   UserScriptList content_scripts = extension->content_scripts();
   for (UserScriptList::const_iterator script = content_scripts.begin();
     script != content_scripts.end(); ++script) {
-      content_script_list->Append(CreateContentScriptDetailValue(*script,
-          extension->path()));
+      content_script_list->Append(
+          CreateContentScriptDetailValue(*script, extension->path()));
   }
   extension_data->Set(L"content_scripts", content_script_list);
 
diff --git a/chrome/browser/net/file_reader.cc b/chrome/browser/extensions/file_reader.cc
index 9e3041e..955e664 100644
--- a/chrome/browser/net/file_reader.cc
+++ b/chrome/browser/extensions/file_reader.cc
@@ -2,13 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/browser/net/file_reader.h"
+#include "chrome/browser/extensions/file_reader.h"
 
 #include "base/file_util.h"
 #include "chrome/browser/chrome_thread.h"
+#include "chrome/common/extensions/extension_resource.h"
 
-FileReader::FileReader(const FilePath& path, Callback* callback)
-    : path_(path),
+FileReader::FileReader(const ExtensionResource& resource, Callback* callback)
+    : resource_(resource),
       callback_(callback),
       origin_loop_(MessageLoop::current()) {
   DCHECK(callback_);
@@ -21,7 +22,7 @@ void FileReader::Start() {
 
 void FileReader::ReadFileOnBackgroundThread() {
   std::string data;
-  bool success = file_util::ReadFileToString(path_, &data);
+  bool success = file_util::ReadFileToString(resource_.GetFilePath(), &data);
   origin_loop_->PostTask(FROM_HERE, NewRunnableMethod(
       this, &FileReader::RunCallback, success, data));
 }
diff --git a/chrome/browser/net/file_reader.h b/chrome/browser/extensions/file_reader.h
index 7aa52f1..008450e 100644
--- a/chrome/browser/net/file_reader.h
+++ b/chrome/browser/extensions/file_reader.h
@@ -1,27 +1,28 @@
 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-//
-// This file defines an interface for reading a file asynchronously on a
-// background thread.
 
-#ifndef CHROME_BROWSER_NET_FILE_READER_H_
-#define CHROME_BROWSER_NET_FILE_READER_H_
+#ifndef CHROME_BROWSER_EXTENSIONS_FILE_READER_H_
+#define CHROME_BROWSER_EXTENSIONS_FILE_READER_H_
 
 #include <string>
 
-#include "base/file_path.h"
 #include "base/ref_counted.h"
 #include "base/task.h"
+#include "chrome/common/extensions/extension_resource.h"
 
 class MessageLoop;
 
+// This file defines an interface for reading a file asynchronously on a
+// background thread.
+// Consider abstracting out a FilePathProvider (ExtensionResource) and moving
+// back to chrome/browser/net if other subsystems want to use it.
 class FileReader : public base::RefCountedThreadSafe<FileReader> {
  public:
   // Reports success or failure and the data of the file upon success.
   typedef Callback2<bool, const std::string&>::Type Callback;
 
-  FileReader(const FilePath& path, Callback* callback);
+  FileReader(const ExtensionResource& resource, Callback* callback);
 
   // Called to start reading the file on a background thread.  Upon completion,
   // the callback will be notified of the results.
@@ -31,9 +32,9 @@ class FileReader : public base::RefCountedThreadSafe<FileReader> {
   void ReadFileOnBackgroundThread();
   void RunCallback(bool success, const std::string& data);
 
-  FilePath path_;
+  ExtensionResource resource_;
   Callback* callback_;
   MessageLoop* origin_loop_;
 };
 
-#endif  // CHROME_BROWSER_NET_FILE_READER_H_
+#endif  // CHROME_BROWSER_EXTENSIONS_FILE_READER_H_
diff --git a/chrome/browser/net/file_reader_unittest.cc b/chrome/browser/extensions/file_reader_unittest.cc
index 72c3f42..bf16b71 100644
--- a/chrome/browser/net/file_reader_unittest.cc
+++ b/chrome/browser/extensions/file_reader_unittest.cc
@@ -2,12 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/message_loop.h"
 #include "base/path_service.h"
 #include "chrome/browser/chrome_thread.h"
-#include "chrome/browser/net/file_reader.h"
+#include "chrome/browser/extensions/file_reader.h"
 #include "chrome/common/chrome_paths.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
@@ -48,6 +50,7 @@ class Receiver {
 void RunBasicTest(const char* filename) {
   FilePath path;
   PathService::Get(chrome::DIR_TEST_DATA, &path);
+  ExtensionResource resource(path, FilePath().AppendASCII(filename));
   path = path.AppendASCII(filename);
 
   std::string file_contents;
@@ -56,7 +59,7 @@ void RunBasicTest(const char* filename) {
   Receiver receiver;
 
   scoped_refptr<FileReader> file_reader(
-      new FileReader(path, receiver.NewCallback()));
+      new FileReader(resource, receiver.NewCallback()));
   file_reader->Start();
 
   MessageLoop::current()->Run();
@@ -76,12 +79,14 @@ TEST_F(FileReaderTest, BiggerFile) {
 TEST_F(FileReaderTest, NonExistantFile) {
   FilePath path;
   PathService::Get(chrome::DIR_TEST_DATA, &path);
+  ExtensionResource resource(path, FilePath(
+      FILE_PATH_LITERAL("file_that_does_not_exist")));
   path = path.AppendASCII("file_that_does_not_exist");
 
   Receiver receiver;
 
   scoped_refptr<FileReader> file_reader(
-      new FileReader(path, receiver.NewCallback()));
+      new FileReader(resource, receiver.NewCallback()));
   file_reader->Start();
 
   MessageLoop::current()->Run();
diff --git a/chrome/browser/image_loading_tracker.cc b/chrome/browser/extensions/image_loading_tracker.cc
index 423e5fd..e141391 100644
--- a/chrome/browser/image_loading_tracker.cc
+++ b/chrome/browser/extensions/image_loading_tracker.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "chrome/browser/image_loading_tracker.h"
+#include "chrome/browser/extensions/image_loading_tracker.h"
 
 #include "app/gfx/favicon_size.h"
 #include "base/file_util.h"
@@ -12,6 +12,7 @@
 #include "base/task.h"
 #include "base/thread.h"
 #include "chrome/browser/browser_process.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "skia/ext/image_operations.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "webkit/glue/image_decoder.h"
@@ -29,11 +30,11 @@ class ImageLoadingTracker::LoadImageTask : public Task {
   // decode it. |path| is the path to load the image from. |index| is an
   // identifier for the image that we pass back to the caller.
   LoadImageTask(ImageLoadingTracker* tracker,
-                const FilePath& path,
+                const ExtensionResource& resource,
                 size_t index)
     : callback_loop_(MessageLoop::current()),
       tracker_(tracker),
-      path_(path),
+      resource_(resource),
       index_(index) {}
 
   void ReportBack(SkBitmap* image) {
@@ -47,8 +48,8 @@ class ImageLoadingTracker::LoadImageTask : public Task {
   virtual void Run() {
     // Read the file from disk.
     std::string file_contents;
-    if (!file_util::PathExists(path_) ||
-        !file_util::ReadFileToString(path_, &file_contents)) {
+    FilePath path = resource_.GetFilePath();
+    if (path.empty() || !file_util::ReadFileToString(path, &file_contents)) {
       ReportBack(NULL);
       return;
     }
@@ -85,8 +86,8 @@ class ImageLoadingTracker::LoadImageTask : public Task {
   // The object that is waiting for us to respond back.
   ImageLoadingTracker* tracker_;
 
-  // The path to the image to load asynchronously.
-  FilePath path_;
+  // The image resource to load asynchronously.
+  ExtensionResource resource_;
 
   // The index of the icon being loaded.
   size_t index_;
@@ -95,9 +96,9 @@ class ImageLoadingTracker::LoadImageTask : public Task {
 ////////////////////////////////////////////////////////////////////////////////
 // ImageLoadingTracker
 
-void ImageLoadingTracker::PostLoadImageTask(FilePath path) {
+void ImageLoadingTracker::PostLoadImageTask(const ExtensionResource& resource) {
   MessageLoop* file_loop = g_browser_process->file_thread()->message_loop();
-  file_loop->PostTask(FROM_HERE, new LoadImageTask(this, path,
+  file_loop->PostTask(FROM_HERE, new LoadImageTask(this, resource,
                                                    posted_count_++));
 }
 
diff --git a/chrome/browser/image_loading_tracker.h b/chrome/browser/extensions/image_loading_tracker.h
index 7265b63..9732a00 100644
--- a/chrome/browser/image_loading_tracker.h
+++ b/chrome/browser/extensions/image_loading_tracker.h
@@ -2,18 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_
-#define CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_
+#ifndef CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
+#define CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
 
 #include "base/ref_counted.h"
 
-class FilePath;
+class ExtensionResource;
 class SkBitmap;
 
 // The views need to load their icons asynchronously but might be deleted before
 // the images have loaded. This class stays alive while the request is in
 // progress (manages its own lifetime) and keeps track of whether the view still
 // cares about the icon loading.
+// Consider abstracting out a FilePathProvider (ExtensionResource) and moving
+// back to chrome/browser/ if other subsystems want to use it.
 class ImageLoadingTracker
   : public base::RefCountedThreadSafe<ImageLoadingTracker> {
  public:
@@ -40,10 +42,10 @@ class ImageLoadingTracker
     observer_ = NULL;
   }
 
-  // Specify path of image to load.  This method must be called a number of
+  // Specify image resource to load.  This method must be called a number of
   // times equal to the |image_count| arugment to the constructor.  Calling it
   // any more or less than that is an error.
-  void PostLoadImageTask(FilePath path);
+  void PostLoadImageTask(const ExtensionResource& resource);
 
  private:
   class LoadImageTask;
@@ -69,4 +71,4 @@ class ImageLoadingTracker
   DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker);
 };
 
-#endif  // CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_
+#endif  // CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
diff --git a/chrome/browser/extensions/user_script_master.cc b/chrome/browser/extensions/user_script_master.cc
index b4130c8..f58a9e6 100644
--- a/chrome/browser/extensions/user_script_master.cc
+++ b/chrome/browser/extensions/user_script_master.cc
@@ -136,20 +136,20 @@ void UserScriptMaster::ScriptReloader::NotifyMaster(
 
 static bool LoadScriptContent(UserScript::File* script_file) {
   std::string content;
-  if (!file_util::ReadFileToString(script_file->path(), &content)) {
-    LOG(WARNING) << "Failed to load user script file: "
-                 << script_file->path().value();
+  FilePath path = script_file->resource().GetFilePath();
+  if (path.empty() || !file_util::ReadFileToString(path, &content)) {
+    LOG(WARNING) << "Failed to load user script file: " << path.value();
     return false;
   }
 
   script_file->set_content(content);
-  LOG(INFO) << "Loaded user script file: " << script_file->path().value();
+  LOG(INFO) << "Loaded user script file: " << path.value();
   return true;
 }
 
 void UserScriptMaster::ScriptReloader::LoadScriptsFromDirectory(
     const FilePath& script_dir, UserScriptList* result) {
-  // Clear the list. We will populate it with the scrips found in script_dir.
+  // Clear the list. We will populate it with the scripts found in script_dir.
   result->clear();
 
   // Find all the scripts in |script_dir|.
@@ -168,7 +168,8 @@ void UserScriptMaster::ScriptReloader::LoadScriptsFromDirectory(
       // Push single js file in this UserScript.
       GURL url(std::string(chrome::kUserScriptScheme) + ":/" +
           net::FilePathToFileURL(file).ExtractFileName());
-      user_script.js_scripts().push_back(UserScript::File(file, url));
+      ExtensionResource resource(script_dir, file.BaseName());
+      user_script.js_scripts().push_back(UserScript::File(resource, url));
       UserScript::File& script_file = user_script.js_scripts().back();
       if (!LoadScriptContent(&script_file))
         result->pop_back();
diff --git a/chrome/browser/gtk/location_bar_view_gtk.cc b/chrome/browser/gtk/location_bar_view_gtk.cc
index a728022..ee6424c 100644
--- a/chrome/browser/gtk/location_bar_view_gtk.cc
+++ b/chrome/browser/gtk/location_bar_view_gtk.cc
@@ -695,7 +695,7 @@ LocationBarViewGtk::PageActionViewGtk::PageActionViewGtk(
   tracker_ = new ImageLoadingTracker(this, icon_paths.size());
   for (std::vector<std::string>::const_iterator iter = icon_paths.begin();
        iter != icon_paths.end(); ++iter) {
-    tracker_->PostLoadImageTask(extension->GetResourcePath(*iter));
+    tracker_->PostLoadImageTask(extension->GetResource(*iter));
   }
 }
 
diff --git a/chrome/browser/gtk/location_bar_view_gtk.h b/chrome/browser/gtk/location_bar_view_gtk.h
index bb86a69..3fe531a 100644
--- a/chrome/browser/gtk/location_bar_view_gtk.h
+++ b/chrome/browser/gtk/location_bar_view_gtk.h
@@ -15,7 +15,7 @@
 #include "base/scoped_vector.h"
 #include "chrome/browser/autocomplete/autocomplete_edit.h"
 #include "chrome/browser/autocomplete/autocomplete_edit_view_gtk.h"
-#include "chrome/browser/image_loading_tracker.h"
+#include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/location_bar.h"
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/notification_registrar.h"
diff --git a/chrome/browser/views/browser_actions_container.cc b/chrome/browser/views/browser_actions_container.cc
index 9fdd2fd..4a246f2 100644
--- a/chrome/browser/views/browser_actions_container.cc
+++ b/chrome/browser/views/browser_actions_container.cc
@@ -10,7 +10,7 @@
 #include "chrome/browser/extensions/extension_browser_event_router.h"
 #include "chrome/browser/extensions/extensions_service.h"
 #include "chrome/browser/extensions/extension_tabs_module.h"
-#include "chrome/browser/image_loading_tracker.h"
+#include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/profile.h"
 #include "chrome/browser/views/extensions/extension_popup.h"
 #include "chrome/browser/views/toolbar_view.h"
@@ -129,8 +129,7 @@ BrowserActionButton::BrowserActionButton(
   tracker_ = new ImageLoadingTracker(this, icon_paths.size());
   for (std::vector<std::string>::const_iterator iter = icon_paths.begin();
        iter != icon_paths.end(); ++iter) {
-    FilePath path = extension->GetResourcePath(*iter);
-    tracker_->PostLoadImageTask(path);
+    tracker_->PostLoadImageTask(extension->GetResource(*iter));
   }
 
   registrar_.Add(this, NotificationType::EXTENSION_BROWSER_ACTION_UPDATED,
@@ -251,7 +250,7 @@ class BrowserActionView : public views::View {
 
  private:
   virtual void Layout();
-   
+
   // Override PaintChildren so that we can paint the badge on top of children.
   virtual void PaintChildren(gfx::Canvas* canvas);
 
@@ -270,7 +269,7 @@ void BrowserActionView::Layout() {
   button_->SetBounds(0, kControlVertOffset, width(),
                      height() - 2 * kControlVertOffset);
 }
-   
+
 void BrowserActionView::PaintChildren(gfx::Canvas* canvas) {
   View::PaintChildren(canvas);
 
diff --git a/chrome/browser/views/location_bar_view.cc b/chrome/browser/views/location_bar_view.cc
index ee8eb90..b7a97a7 100644
--- a/chrome/browser/views/location_bar_view.cc
+++ b/chrome/browser/views/location_bar_view.cc
@@ -1204,8 +1204,7 @@ LocationBarView::PageActionImageView::PageActionImageView(
   tracker_ = new ImageLoadingTracker(this, icon_paths.size());
   for (std::vector<std::string>::const_iterator iter = icon_paths.begin();
        iter != icon_paths.end(); ++iter) {
-    FilePath path = extension->GetResourcePath(*iter);
-    tracker_->PostLoadImageTask(path);
+    tracker_->PostLoadImageTask(extension->GetResource(*iter));
   }
 }
 
diff --git a/chrome/browser/views/location_bar_view.h b/chrome/browser/views/location_bar_view.h
index b315e75..fb8b249 100644
--- a/chrome/browser/views/location_bar_view.h
+++ b/chrome/browser/views/location_bar_view.h
@@ -11,7 +11,7 @@
 #include "app/gfx/font.h"
 #include "base/gfx/rect.h"
 #include "chrome/browser/autocomplete/autocomplete_edit.h"
-#include "chrome/browser/image_loading_tracker.h"
+#include "chrome/browser/extensions/image_loading_tracker.h"
 #include "chrome/browser/location_bar.h"
 #include "chrome/browser/tab_contents/tab_contents.h"
 #include "chrome/browser/toolbar_model.h"
diff --git a/chrome/chrome.gyp b/chrome/chrome.gyp
index fb39caf..07b32bd 100755
--- a/chrome/chrome.gyp
+++ b/chrome/chrome.gyp
@@ -499,6 +499,8 @@
         'common/extensions/extension_action.h',
         'common/extensions/extension_message_bundle.cc',
         'common/extensions/extension_message_bundle.h',
+        'common/extensions/extension_resource.cc',
+        'common/extensions/extension_resource.h',
         'common/extensions/extension_unpacker.cc',
         'common/extensions/extension_unpacker.h',
         'common/extensions/update_manifest.cc',
@@ -1281,8 +1283,12 @@
         'browser/extensions/external_registry_extension_provider_win.h',
         'browser/extensions/external_pref_extension_provider.cc',
         'browser/extensions/external_pref_extension_provider.h',
+        'browser/extensions/file_reader.cc',
+        'browser/extensions/file_reader.h',
         'browser/extensions/gtk_theme_preview_infobar_delegate.cc',
         'browser/extensions/gtk_theme_preview_infobar_delegate.h',
+        'browser/extensions/image_loading_tracker.cc',
+        'browser/extensions/image_loading_tracker.h',
         'browser/extensions/pack_extension_job.cc',
         'browser/extensions/pack_extension_job.h',
         'browser/extensions/sandboxed_extension_unpacker.cc',
@@ -1553,8 +1559,6 @@
         'browser/icon_manager_linux.cc',
         'browser/icon_manager_mac.mm',
         'browser/icon_manager_win.cc',
-        'browser/image_loading_tracker.cc',
-        'browser/image_loading_tracker.h',
         'browser/ime_input.cc',
         'browser/ime_input.h',
         'browser/importer/firefox2_importer.cc',
@@ -1660,8 +1664,6 @@
         'browser/net/dns_host_info.h',
         'browser/net/dns_master.cc',
         'browser/net/dns_master.h',
-        'browser/net/file_reader.cc',
-        'browser/net/file_reader.h',
         'browser/net/metadata_url_request.cc',
         'browser/net/metadata_url_request.h',
         'browser/net/referrer.cc',
@@ -4251,6 +4253,7 @@
         'browser/extensions/extension_ui_unittest.cc',
         'browser/extensions/extension_updater_unittest.cc',
         'browser/extensions/extensions_service_unittest.cc',
+        'browser/extensions/file_reader_unittest.cc',
         'browser/extensions/user_script_listener_unittest.cc',
         'browser/extensions/user_script_master_unittest.cc',
         'browser/find_backend_unittest.cc',
@@ -4303,7 +4306,6 @@
         'browser/net/chrome_url_request_context_unittest.cc',
         'browser/net/dns_host_info_unittest.cc',
         'browser/net/dns_master_unittest.cc',
-        'browser/net/file_reader_unittest.cc',
         'browser/net/resolve_proxy_msg_helper_unittest.cc',
         'browser/net/test_url_fetcher_factory.cc',
         'browser/net/test_url_fetcher_factory.h',
@@ -4368,6 +4370,7 @@
         'common/child_process_logging_mac_unittest.mm',
         'common/chrome_plugin_unittest.cc',
         'common/common_param_traits_unittest.cc',
+        'common/extensions/extension_resource_unittest.cc',
         'common/extensions/extension_unittest.cc',
         'common/extensions/extension_message_bundle_unittest.cc',
         'common/extensions/update_manifest_unittest.cc',
diff --git a/chrome/common/extensions/extension.cc b/chrome/common/extensions/extension.cc
index f00db65..ccfe787 100644
--- a/chrome/common/extensions/extension.cc
+++ b/chrome/common/extensions/extension.cc
@@ -13,6 +13,7 @@
 #include "base/stl_util-inl.h"
 #include "base/third_party/nss/blapi.h"
 #include "base/third_party/nss/sha256.h"
+#include "chrome/browser/extensions/extension_l10n_util.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/extensions/extension_constants.h"
 #include "chrome/common/extensions/extension_error_reporter.h"
@@ -21,7 +22,6 @@
 #include "chrome/common/notification_service.h"
 #include "chrome/common/url_constants.h"
 #include "net/base/base64.h"
-#include "net/base/net_util.h"
 
 #if defined(OS_WIN)
 #include "base/registry.h"
@@ -282,8 +282,8 @@ bool Extension::LoadUserScriptHelper(const DictionaryValue* content_script,
       }
       // TODO(georged): Make GetResourceURL accept wstring too
       GURL url = GetResourceURL(WideToUTF8(relative));
-      FilePath path = GetResourcePath(WideToUTF8(relative));
-      result->js_scripts().push_back(UserScript::File(path, url));
+      ExtensionResource resource = GetResource(WideToUTF8(relative));
+      result->js_scripts().push_back(UserScript::File(resource, url));
     }
   }
 
@@ -299,8 +299,8 @@ bool Extension::LoadUserScriptHelper(const DictionaryValue* content_script,
       }
       // TODO(georged): Make GetResourceURL accept wstring too
       GURL url = GetResourceURL(WideToUTF8(relative));
-      FilePath path = GetResourcePath(WideToUTF8(relative));
-      result->css_scripts().push_back(UserScript::File(path, url));
+      ExtensionResource resource = GetResource(WideToUTF8(relative));
+      result->css_scripts().push_back(UserScript::File(resource, url));
     }
   }
 
@@ -427,37 +427,11 @@ bool Extension::ContainsNonThemeKeys(const DictionaryValue& source) {
 }
 
 // static
-FilePath Extension::GetResourcePath(const FilePath& extension_path,
-                                    const std::string& relative_path) {
-  // Build up a file:// URL and convert that back to a FilePath.  This avoids
-  // URL encoding and path separator issues.
-
-  // Convert the extension's root to a file:// URL.
-  GURL extension_url = net::FilePathToFileURL(extension_path);
-  if (!extension_url.is_valid())
-    return FilePath();
-
-  // Append the requested path.
-  GURL::Replacements replacements;
-  std::string new_path(extension_url.path());
-  new_path += "/";
-  new_path += relative_path;
-  replacements.SetPathStr(new_path);
-  GURL file_url = extension_url.ReplaceComponents(replacements);
-  if (!file_url.is_valid())
-    return FilePath();
-
-  // Convert the result back to a FilePath.
-  FilePath ret_val;
-  if (!net::FileURLToFilePath(file_url, &ret_val))
-    return FilePath();
-
-  // Double-check that the path we ended up with is actually inside the
-  // extension root.
-  if (!extension_path.IsParent(ret_val))
-    return FilePath();
-
-  return ret_val;
+ExtensionResource Extension::GetResource(const FilePath& extension_path,
+                                         const std::string& relative_path) {
+  FilePath relative_resource_path;
+  return ExtensionResource(extension_path,
+                           relative_resource_path.AppendASCII(relative_path));
 }
 
 Extension::Extension(const FilePath& path)
@@ -1119,12 +1093,12 @@ void Extension::SetBackgroundPageReady() {
       NotificationService::NoDetails());
 }
 
-FilePath Extension::GetIconPath(Icons icon) {
+ExtensionResource Extension::GetIconPath(Icons icon) {
   std::map<int, std::string>::const_iterator iter =
       icons_.find(Extension::EXTENSION_ICON_LARGE);
   if (iter == icons_.end())
-    return FilePath();
-  return GetResourcePath(iter->second);
+    return ExtensionResource();
+  return GetResource(iter->second);
 }
 
 bool Extension::CanAccessHost(const GURL& url) const {
diff --git a/chrome/common/extensions/extension.h b/chrome/common/extensions/extension.h
index c01d948..57337de 100644
--- a/chrome/common/extensions/extension.h
+++ b/chrome/common/extensions/extension.h
@@ -17,6 +17,7 @@
 #include "chrome/browser/extensions/user_script_master.h"
 #include "chrome/common/extensions/extension_action.h"
 #include "chrome/common/extensions/extension_message_bundle.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/extensions/user_script.h"
 #include "chrome/common/extensions/url_pattern.h"
 #include "googleurl/src/gurl.h"
@@ -132,15 +133,14 @@ class Extension {
     return GetResourceURL(url(), relative_path);
   }
 
-  // Returns an absolute path to a resource inside of an extension. The
-  // |extension_path| argument should be the path() from an Extension object.
-  // The |relative_path| can be untrusted user input. The returned path will
-  // either be empty or a child of extension_path.
+  // Returns an extension resource object. The |extension_path| argument should
+  // be the path() from an Extension object.
+  // The |relative_path| can be untrusted user input.
   // NOTE: Static so that it can be used from multiple threads.
-  static FilePath GetResourcePath(const FilePath& extension_path,
-                                  const std::string& relative_path);
-  FilePath GetResourcePath(const std::string& relative_path) {
-    return GetResourcePath(path(), relative_path);
+  static ExtensionResource GetResource(const FilePath& extension_path,
+                                       const std::string& relative_path);
+  ExtensionResource GetResource(const std::string& relative_path) {
+    return GetResource(path(), relative_path);
   }
 
   // |input| is expected to be the text of an rsa public or private key. It
@@ -243,7 +243,7 @@ class Extension {
 
   // Returns an absolute path to the given icon inside of the extension. Returns
   // an empty FilePath if the extension does not have that icon.
-  FilePath GetIconPath(Icons icon);
+  ExtensionResource GetIconPath(Icons icon);
 
   const DictionaryValue* manifest_value() const {
     return manifest_value_.get();
diff --git a/chrome/common/extensions/extension_resource.cc b/chrome/common/extensions/extension_resource.cc
new file mode 100644
index 0000000..f64354f
--- /dev/null
+++ b/chrome/common/extensions/extension_resource.cc
@@ -0,0 +1,100 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/common/extensions/extension_resource.h"
+
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/string_util.h"
+#include "chrome/browser/extensions/extension_l10n_util.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/net_util.h"
+
+ExtensionResource::ExtensionResource() {
+}
+
+ExtensionResource::ExtensionResource(const FilePath& extension_root,
+                                     const FilePath& relative_path)
+    : extension_root_(extension_root),
+      relative_path_(relative_path) {
+}
+
+const FilePath& ExtensionResource::GetFilePath() const {
+  if (extension_root_.empty() || relative_path_.empty())
+    return full_resource_path_;
+
+  // We've already checked, just return last value.
+  if (!full_resource_path_.empty())
+    return full_resource_path_;
+
+  // Stat l10n file, and return new path if it exists.
+  FilePath l10n_relative_path =
+    extension_l10n_util::GetL10nRelativePath(relative_path_);
+  full_resource_path_ = CombinePathsSafely(extension_root_, l10n_relative_path);
+  if (file_util::PathExists(full_resource_path_)) {
+    return full_resource_path_;
+  }
+
+  // Fall back to root resource.
+  full_resource_path_ = CombinePathsSafely(extension_root_, relative_path_);
+  return full_resource_path_;
+}
+
+FilePath ExtensionResource::CombinePathsSafely(
+    const FilePath& extension_path,
+    const FilePath& relative_resource_path) const {
+  // Build up a file:// URL and convert that back to a FilePath.  This avoids
+  // URL encoding and path separator issues.
+
+  // Convert the extension's root to a file:// URL.
+  GURL extension_url = net::FilePathToFileURL(extension_path);
+  if (!extension_url.is_valid())
+    return FilePath();
+
+  // Append the requested path.
+  std::string relative_path =
+    WideToUTF8(relative_resource_path.ToWStringHack());
+  GURL::Replacements replacements;
+  std::string new_path(extension_url.path());
+  new_path += "/";
+  new_path += relative_path;
+  replacements.SetPathStr(new_path);
+  GURL file_url = extension_url.ReplaceComponents(replacements);
+  if (!file_url.is_valid())
+    return FilePath();
+
+  // Convert the result back to a FilePath.
+  FilePath ret_val;
+  if (!net::FileURLToFilePath(file_url, &ret_val))
+    return FilePath();
+
+  // Double-check that the path we ended up with is actually inside the
+  // extension root.
+  if (!extension_path.IsParent(ret_val))
+    return FilePath();
+
+  return ret_val;
+}
+
+// Unittesting helpers.
+FilePath::StringType ExtensionResource::NormalizeSeperators(
+    FilePath::StringType path) const {
+#if defined(FILE_PATH_USES_WIN_SEPARATORS)
+  FilePath::StringType ret_val;
+  for (size_t i = 0; i < path.length(); i++) {
+    if (FilePath::IsSeparator(path[i]))
+      path[i] = FilePath::kSeparators[0];
+  }
+#endif  // FILE_PATH_USES_WIN_SEPARATORS
+  return path;
+}
+
+bool ExtensionResource::ComparePathWithDefault(const FilePath& path) const {
+  if (NormalizeSeperators(path.value()) ==
+    NormalizeSeperators(full_resource_path_.value())) {
+    return true;
+  } else {
+    return false;
+  }
+}
diff --git a/chrome/common/extensions/extension_resource.h b/chrome/common/extensions/extension_resource.h
new file mode 100644
index 0000000..7d6e70c6
--- /dev/null
+++ b/chrome/common/extensions/extension_resource.h
@@ -0,0 +1,49 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_EXTENSIONS_EXTENSION_RESOURCE_H_
+#define CHROME_COMMON_EXTENSIONS_EXTENSION_RESOURCE_H_
+
+#include "base/file_path.h"
+
+// Represents a resource inside an extension. For example, an image, or a
+// JavaScript file. This is more complicated than just a simple FilePath
+// because extension resources can come from multiple physical file locations
+// depending on locale.
+class ExtensionResource {
+ public:
+  ExtensionResource();
+
+  ExtensionResource(const FilePath& extension_root,
+                    const FilePath& relative_path);
+
+  // Returns actual path to the resource (default or locale specific).
+  // *** MIGHT HIT FILESYSTEM. Do not call on UI thread! ***
+  const FilePath& GetFilePath() const;
+
+  // Getters
+  const FilePath& extension_root() const { return extension_root_; }
+  const FilePath& relative_path() const { return relative_path_; }
+
+  // Unittest helpers.
+  FilePath::StringType NormalizeSeperators(FilePath::StringType path) const;
+  bool ComparePathWithDefault(const FilePath& path) const;
+
+ private:
+  // Returns normalized full path to the resource.
+  // Resource doesn't have to exist.
+  FilePath CombinePathsSafely(const FilePath& extension_root,
+                              const FilePath& relative_path) const;
+
+  // Extension root.
+  FilePath extension_root_;
+
+  // Relative path to resource.
+  FilePath relative_path_;
+
+  // Full path to extension resource. Starts empty.
+  mutable FilePath full_resource_path_;
+};
+
+#endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_RESOURCE_H_
diff --git a/chrome/common/extensions/extension_resource_unittest.cc b/chrome/common/extensions/extension_resource_unittest.cc
new file mode 100644
index 0000000..bd92bd9
--- /dev/null
+++ b/chrome/common/extensions/extension_resource_unittest.cc
@@ -0,0 +1,74 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <algorithm>
+
+#include "app/l10n_util.h"
+#include "base/file_util.h"
+#include "base/path_service.h"
+#include "base/scoped_temp_dir.h"
+#include "chrome/common/chrome_paths.h"
+#include "chrome/common/extensions/extension.h"
+#include "chrome/common/extensions/extension_resource.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(ExtensionResourceTest, CreateEmptyResource) {
+  ExtensionResource resource;
+
+  EXPECT_TRUE(resource.extension_root().empty());
+  EXPECT_TRUE(resource.relative_path().empty());
+  EXPECT_TRUE(resource.GetFilePath().empty());
+}
+
+const FilePath::StringType ToLower(const FilePath::StringType& in_str) {
+  FilePath::StringType str(in_str);
+  std::transform(str.begin(), str.end(), str.begin(), tolower);
+  return str;
+}
+
+TEST(ExtensionResourceTest, CreateWithMissingResourceOnDisk) {
+  FilePath root_path;
+  ASSERT_TRUE(PathService::Get(chrome::DIR_TEST_DATA, &root_path));
+  FilePath relative_path;
+  relative_path = relative_path.AppendASCII("cira.js");
+  ExtensionResource resource(root_path, relative_path);
+
+  EXPECT_EQ(root_path.value(), resource.extension_root().value());
+  EXPECT_EQ(relative_path.value(), resource.relative_path().value());
+  EXPECT_EQ(root_path.Append(relative_path).value(),
+    ToLower(resource.GetFilePath().value()));
+
+  EXPECT_FALSE(resource.GetFilePath().empty());
+}
+
+TEST(ExtensionResourceTest, CreateWithBothResourcesOnDisk) {
+  ScopedTempDir temp;
+  ASSERT_TRUE(temp.CreateUniqueTempDir());
+
+  const char* filename = "res.ico";
+  FilePath root_resource = temp.path().AppendASCII(filename);
+  std::string data = "some foo";
+  ASSERT_TRUE(file_util::WriteFile(root_resource.AppendASCII(filename),
+      data.c_str(), data.length()));
+
+  FilePath l10n_path = temp.path().AppendASCII(Extension::kLocaleFolder);
+  ASSERT_TRUE(file_util::CreateDirectory(l10n_path));
+
+  static std::string current_locale = l10n_util::GetApplicationLocale(L"");
+  std::replace(current_locale.begin(), current_locale.end(), '-', '_');
+  l10n_path = l10n_path.AppendASCII(current_locale);
+  ASSERT_TRUE(file_util::CreateDirectory(l10n_path));
+
+  ASSERT_TRUE(file_util::WriteFile(l10n_path.AppendASCII(filename),
+      data.c_str(), data.length()));
+
+  FilePath path;
+  ExtensionResource resource(temp.path(), FilePath().AppendASCII(filename));
+  FilePath resolved_path = resource.GetFilePath();
+
+  EXPECT_EQ(l10n_path.AppendASCII(filename).value(), resolved_path.value());
+  EXPECT_EQ(temp.path().value(), resource.extension_root().value());
+  EXPECT_EQ(FilePath().AppendASCII(filename).value(),
+      resource.relative_path().value());
+}
diff --git a/chrome/common/extensions/extension_unittest.cc b/chrome/common/extensions/extension_unittest.cc
index 466f27a..26cf648 100644
--- a/chrome/common/extensions/extension_unittest.cc
+++ b/chrome/common/extensions/extension_unittest.cc
@@ -262,15 +262,6 @@ TEST(ExtensionTest, GetResourceURLAndPath) {
             Extension::GetResourceURL(extension.url(), "bar/../baz.js").spec());
   EXPECT_EQ(extension.url().spec() + "baz.js",
             Extension::GetResourceURL(extension.url(), "../baz.js").spec());
-
-  EXPECT_EQ(path.Append(FILE_PATH_LITERAL("bar"))
-                .Append(FILE_PATH_LITERAL("baz.js")).value(),
-            Extension::GetResourcePath(extension.path(), "bar/baz.js").value());
-  EXPECT_EQ(path.Append(FILE_PATH_LITERAL("baz.js")).value(),
-            Extension::GetResourcePath(extension.path(), "bar/../baz.js")
-                .value());
-  EXPECT_EQ(FilePath().value(),
-            Extension::GetResourcePath(extension.path(), "../baz.js").value());
 }
 
 TEST(ExtensionTest, LoadPageActionHelper) {
diff --git a/chrome/common/extensions/user_script.h b/chrome/common/extensions/user_script.h
index 4b571799..30807e8 100644
--- a/chrome/common/extensions/user_script.h
+++ b/chrome/common/extensions/user_script.h
@@ -10,6 +10,7 @@
 
 #include "base/file_path.h"
 #include "base/string_piece.h"
+#include "chrome/common/extensions/extension_resource.h"
 #include "chrome/common/extensions/url_pattern.h"
 #include "googleurl/src/gurl.h"
 
@@ -34,14 +35,16 @@ class UserScript {
   // Holds actual script file info.
   class File {
    public:
-    File(const FilePath& path, const GURL& url):
-         path_(path),
+    File(const ExtensionResource& resource, const GURL& url):
+         resource_(resource),
          url_(url) {
     }
     File() {}
 
-    const FilePath& path() const { return path_; }
-    void set_path(const FilePath& path) { path_ = path; }
+    const ExtensionResource& resource() const { return resource_; }
+    void set_resource(const ExtensionResource& resource) {
+      resource_ = resource;
+    }
 
     const GURL& url() const { return url_; }
     void set_url(const GURL& url) { url_ = url; }
@@ -61,14 +64,14 @@ class UserScript {
       content_.assign(content.begin(), content.end());
     }
 
-    // Serialization support. The content and path_ member will not be
+    // Serialization support. The content and resource_ member will not be
     // serialized!
     void Pickle(::Pickle* pickle) const;
     void Unpickle(const ::Pickle& pickle, void** iter);
 
    private:
-    // Where is the script file lives on the disk.
-    FilePath path_;
+    // Where the script file lives on the disk.
+    ExtensionResource resource_;
 
     // The url to this scipt file.
     GURL url_;
diff --git a/chrome/common/extensions/user_script_unittest.cc b/chrome/common/extensions/user_script_unittest.cc
index 62fa0a3..0c0bac9 100644
--- a/chrome/common/extensions/user_script_unittest.cc
+++ b/chrome/common/extensions/user_script_unittest.cc
@@ -78,13 +78,16 @@ TEST(UserScriptTest, Pickle) {
 
   UserScript script1;
   script1.js_scripts().push_back(UserScript::File(
-      FilePath(FILE_PATH_LITERAL("c:\\foo\\foo.user.js")),
+      ExtensionResource(FilePath(FILE_PATH_LITERAL("c:\\foo\\")),
+                        FilePath(FILE_PATH_LITERAL("foo.user.js"))),
       GURL("chrome-user-script:/foo.user.js")));
   script1.css_scripts().push_back(UserScript::File(
-      FilePath(FILE_PATH_LITERAL("c:\\foo\\foo.user.css")),
+      ExtensionResource(FilePath(FILE_PATH_LITERAL("c:\\foo\\")),
+                        FilePath(FILE_PATH_LITERAL("foo.user.css"))),
       GURL("chrome-user-script:/foo.user.css")));
   script1.css_scripts().push_back(UserScript::File(
-      FilePath(FILE_PATH_LITERAL("c:\\foo\\foo2.user.css")),
+      ExtensionResource(FilePath(FILE_PATH_LITERAL("c:\\foo\\")),
+                        FilePath(FILE_PATH_LITERAL("foo2.user.css"))),
       GURL("chrome-user-script:/foo2.user.css")));
   script1.set_run_location(UserScript::DOCUMENT_START);