chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/extension_message_bubble_controller.h

 // Copyright (c) 2013 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_MESSAGE_BUBBLE_CONTROLLER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_BUBBLE_CONTROLLER_H_
 
 #include <stddef.h>
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/scoped_observer.h"
 #include "chrome/browser/ui/browser_list_observer.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
 #include "extensions/common/extension.h"
 
 class Browser;
 class BrowserList;
 class ExtensionService;
 class ToolbarActionsModel;
 class Profile;
 
 namespace extensions {
 
-class ExtensionPrefs;
 class ExtensionRegistry;
 
 class ExtensionMessageBubbleController : public chrome::BrowserListObserver {
  public:
   // UMA histogram constants.
   enum BubbleAction {
     ACTION_LEARN_MORE = 0,
     ACTION_EXECUTE,
     ACTION_DISMISS_USER_ACTION,
     ACTION_DISMISS_DEACTIVATION,
@@ skipping 178 matching lines @@
   bool is_active_bubble_;
 
   ScopedObserver<BrowserList, BrowserListObserver> browser_list_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionMessageBubbleController);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_MESSAGE_BUBBLE_CONTROLLER_H_