Add a class to replace ImageLoadingTracker with a nicer API.

chrome/browser/extensions/extension_system.h

 // Copyright (c) 2012 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_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_H_
 
 #include <string>
 
 #include "base/memory/ref_counted.h"
@@ skipping 136 matching lines @@
 
   virtual void InitForRegularProfile(bool extensions_enabled) OVERRIDE;
   virtual void InitForOTRProfile() OVERRIDE;
 
   virtual ExtensionService* extension_service() OVERRIDE;  // shared
   virtual ManagementPolicy* management_policy() OVERRIDE;  // shared
   virtual UserScriptMaster* user_script_master() OVERRIDE;  // shared
   virtual ExtensionDevToolsManager* devtools_manager() OVERRIDE;
   virtual ExtensionProcessManager* process_manager() OVERRIDE;
   virtual AlarmManager* alarm_manager() OVERRIDE;
-  virtual StateStore* state_store() OVERRIDE;
-  virtual ShellWindowGeometryCache* shell_window_geometry_cache() OVERRIDE;
+  virtual StateStore* state_store() OVERRIDE;  // shared
+  virtual ShellWindowGeometryCache* shell_window_geometry_cache()
+      OVERRIDE;  // shared
   virtual LazyBackgroundTaskQueue* lazy_background_task_queue()
       OVERRIDE;  // shared
   virtual ExtensionInfoMap* info_map() OVERRIDE;  // shared
   virtual MessageService* message_service() OVERRIDE;  // shared
   virtual EventRouter* event_router() OVERRIDE;  // shared
   virtual RulesRegistryService* rules_registry_service()
       OVERRIDE;  // shared
   virtual ApiResourceManager<SerialConnection>* serial_connection_manager()
       OVERRIDE;
   virtual ApiResourceManager<Socket>* socket_manager() OVERRIDE;
@@ skipping 74 matching lines @@
   scoped_ptr<ApiResourceManager<
                UsbDeviceResource> > usb_device_resource_manager_;
   scoped_ptr<RulesRegistryService> rules_registry_service_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionSystemImpl);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SYSTEM_H_