content: Cleanup class/struct forward declarations

content/renderer/pepper/renderer_ppapi_host_impl.h

 // Copyright (c) 2012 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_PEPPER_RENDERER_PPAPI_HOST_IMPL_H_
 #define CONTENT_RENDERER_PEPPER_RENDERER_PPAPI_HOST_IMPL_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "content/public/renderer/renderer_ppapi_host.h"
 #include "content/renderer/pepper/content_renderer_pepper_host_factory.h"
 #include "ppapi/host/ppapi_host.h"
 
-namespace IPC {
-class Sender;
-}
-
 namespace ppapi {
 
 namespace proxy {
 class HostDispatcher;
 }
 
 namespace thunk {
 class ResourceCreationAPI;
 }
 
@@ skipping 114 matching lines @@
 
   // The scale between the viewport and dip.
   float viewport_to_dip_scale_ = 1.0f;
 
   DISALLOW_COPY_AND_ASSIGN(RendererPpapiHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_RENDERER_PPAPI_HOST_IMPL_H_