ppapi: Cleanup class/struct forward declarations

ppapi/cpp/dev/video_decoder_client_dev.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 PPAPI_CPP_DEV_VIDEO_DECODER_CLIENT_DEV_H_
 #define PPAPI_CPP_DEV_VIDEO_DECODER_CLIENT_DEV_H_
 
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/dev/pp_video_dev.h"
 #include "ppapi/cpp/instance_handle.h"
 
 namespace pp {
 
 class Instance;
-class VideoDecoder_Dev;
 
 // This class provides a C++ interface for callbacks related to video decoding.
 // It is the C++ counterpart to PPP_VideoDecoder_Dev.
 // You would normally use multiple inheritance to derive from this class in your
 // instance.
 class VideoDecoderClient_Dev {
  public:
   VideoDecoderClient_Dev(Instance* instance);
   virtual ~VideoDecoderClient_Dev();
 
@@ skipping 16 matching lines @@
   virtual void NotifyError(PP_Resource decoder,
                            PP_VideoDecodeError_Dev error) = 0;
 
  private:
   InstanceHandle associated_instance_;
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_VIDEO_DECODER_CLIENT_DEV_H_