Cleanup: Remove more forward declarations in various chrome/browser directories.

chrome/browser/background/background_application_list_model.h

 // Copyright (c) 2011 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_BACKGROUND_BACKGROUND_APPLICATION_LIST_MODEL_H_
 #define CHROME_BROWSER_BACKGROUND_BACKGROUND_APPLICATION_LIST_MODEL_H_
 #pragma once
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/observer_list.h"
 #include "chrome/common/extensions/extension.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class ExtensionService;
-class PrefService;
 class Profile;
 
 // Model for list of Background Applications, that is, Extensions with
 // kBackgroundPermission set, associated with a Profile.
 class BackgroundApplicationListModel : public content::NotificationObserver {
  public:
   // Observer is informed of changes to the model.  Users of the
   // BackgroundApplicationListModel should anticipate that associated data,
   // e. g. the Icon, may exist and yet not be immediately available.  When the
   // data becomes available, OnApplicationDataChanged will be invoked for all
@@ skipping 105 matching lines @@
   ApplicationMap applications_;
   ExtensionList extensions_;
   ObserverList<Observer> observers_;
   Profile* profile_;
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(BackgroundApplicationListModel);
 };
 
 #endif  // CHROME_BROWSER_BACKGROUND_BACKGROUND_APPLICATION_LIST_MODEL_H_