Cleanup: Remove forward declarations in various directories.

content/browser/host_zoom_map.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.
 
 // Maps hostnames to custom zoom levels.  Written on the UI thread and read on
 // any thread.  One instance per browser context.
 
 #ifndef CONTENT_BROWSER_HOST_ZOOM_MAP_H_
 #define CONTENT_BROWSER_HOST_ZOOM_MAP_H_
 #pragma once
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class GURL;
-
 // HostZoomMap needs to be deleted on the UI thread because it listens
 // to notifications on there (and holds a NotificationRegistrar).
 class CONTENT_EXPORT HostZoomMap
     : public content::NotificationObserver,
       public base::RefCountedThreadSafe<
           HostZoomMap, content::BrowserThread::DeleteOnUIThread> {
  public:
   explicit HostZoomMap();
   explicit HostZoomMap(HostZoomMap* original);
 
@@ skipping 72 matching lines @@
   // Used around accesses to |host_zoom_levels_|, |default_zoom_level_| and
   // |temporary_zoom_levels_| to guarantee thread safety.
   mutable base::Lock lock_;
 
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(HostZoomMap);
 };
 
 #endif  // CONTENT_BROWSER_HOST_ZOOM_MAP_H_