Eliminate all UI thread decoding of extension images....

chrome/common/extensions/extension_resource.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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! ***
+  // NOTE: If you need to access ExtensionResources, such as bitmaps, on the UI
+  // thread, please use the ImageLoadingTracker, which uses the File thread.
   const FilePath& GetFilePath() const;
 
   // Static version to avoid creating an instance of ExtensionResource
   // when all we want is the localization code.
   // *** MIGHT HIT FILESYSTEM. Do not call on UI thread! ***
+  // NOTE: If you need to access ExtensionResources, such as bitmaps, on the UI
+  // thread, please use the ImageLoadingTracker, which uses the File thread.
   static FilePath GetFilePath(const FilePath& extension_root,
                               const FilePath& relative_path);
 
   // Getters
   const FilePath& extension_root() const { return extension_root_; }
   const FilePath& relative_path() const { return relative_path_; }
 
-  // Unittest helpers.
+  // Unit test helpers.
   FilePath::StringType NormalizeSeperators(FilePath::StringType path) const;
   bool ComparePathWithDefault(const FilePath& path) const;
 
  private:
   // 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_