content: Cleanup class/struct forward declarations

content/renderer/pepper/pepper_video_decoder_host.h

 // Copyright (c) 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_RENDERER_PEPPER_PEPPER_VIDEO_DECODER_HOST_H_
 #define CONTENT_RENDERER_PEPPER_PEPPER_VIDEO_DECODER_HOST_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 11 matching lines @@
 #include "ppapi/host/host_message_context.h"
 #include "ppapi/host/resource_host.h"
 #include "ppapi/proxy/resource_message_params.h"
 
 namespace base {
 class SharedMemory;
 }
 
 namespace content {
 
-class PPB_Graphics3D_Impl;
 class RendererPpapiHost;
-class RenderViewImpl;
 class VideoDecoderShim;
 
 class CONTENT_EXPORT PepperVideoDecoderHost
     : public ppapi::host::ResourceHost,
       public media::VideoDecodeAccelerator::Client {
  public:
   PepperVideoDecoderHost(RendererPpapiHost* host,
                          PP_Instance instance,
                          PP_Resource resource);
   ~PepperVideoDecoderHost() override;
@@ skipping 102 matching lines @@
   ppapi::host::ReplyMessageContext reset_reply_context_;
 
   bool initialized_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(PepperVideoDecoderHost);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_VIDEO_DECODER_HOST_H_