Cleanup: Remove forward declarations in various directories.

content/renderer/render_thread_impl.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 CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 #define CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 #pragma once
 
 #include <set>
 #include <string>
@@ skipping 13 matching lines @@
 
 class AppCacheDispatcher;
 class AudioInputMessageFilter;
 class AudioMessageFilter;
 class CompositorThread;
 class DBMessageFilter;
 class DevToolsAgentFilter;
 struct DOMStorageMsg_Event_Params;
 class GpuChannelHost;
 class IndexedDBDispatcher;
-class RendererHistogram;
 class RendererWebKitPlatformSupportImpl;
 class SkBitmap;
 class VideoCaptureImplManager;
 struct ViewMsg_New_Params;
 class WebDatabaseObserverImpl;
 
 namespace WebKit {
 class WebStorageEventDispatcher;
 }
 
@@ skipping 189 matching lines @@
   std::set<std::string> v8_extensions_;
 
   scoped_ptr<CompositorThread> compositor_thread_;
 
   ObserverList<content::RenderProcessObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_