content: Cleanup class/struct forward declarations

content/browser/frame_host/render_frame_proxy_host.h

 // Copyright 2014 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_BROWSER_FRAME_HOST_RENDER_FRAME_PROXY_HOST_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_PROXY_HOST_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/browser/site_instance_impl.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
 #include "third_party/WebKit/public/platform/WebFocusType.h"
 
 struct FrameHostMsg_OpenURL_Params;
 struct FrameMsg_PostMessage_Params;
 
 namespace content {
 
 class CrossProcessFrameConnector;
 class FrameTreeNode;
 class RenderProcessHost;
-class RenderFrameHostImpl;
 class RenderViewHostImpl;
 class RenderWidgetHostView;
 
 // When a page's frames are rendered by multiple processes, each renderer has a
 // full copy of the frame tree. It has full RenderFrames for the frames it is
 // responsible for rendering and placeholder objects (i.e., RenderFrameProxies)
 // for frames rendered by other processes.
 //
 // This class is the browser-side host object for the placeholder. Each node in
 // the frame tree has a RenderFrameHost for the active SiteInstance and a set
@@ skipping 116 matching lines @@
   // kept alive as long as any RenderFrameHosts or RenderFrameProxyHosts
   // are associated with it.
   RenderViewHostImpl* render_view_host_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameProxyHost);
 };
 
 }  // namespace
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_PROXY_HOST_H_