Enable fire-and-forget Destroy of HW video decoder, and misc other improvements.

ppapi/thunk/ppb_video_decoder_api.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 PPAPI_THUNK_VIDEO_DECODER_API_H_
 #define PPAPI_THUNK_VIDEO_DECODER_API_H_
 
 #include "ppapi/c/dev/ppb_video_decoder_dev.h"
 
 namespace ppapi {
 namespace thunk {
 
 class PPB_VideoDecoder_API {
  public:
   virtual ~PPB_VideoDecoder_API() {}
 
   virtual int32_t Initialize(PP_Resource context_id,
                              const PP_VideoConfigElement* decoder_config,
                              PP_CompletionCallback callback) = 0;
   virtual int32_t Decode(const PP_VideoBitstreamBuffer_Dev* bitstream_buffer,
                          PP_CompletionCallback callback) = 0;
   virtual void AssignGLESBuffers(uint32_t no_of_buffers,
                                  const PP_GLESBuffer_Dev* buffers) = 0;
   virtual void ReusePictureBuffer(int32_t picture_buffer_id) = 0;
   virtual int32_t Flush(PP_CompletionCallback callback) = 0;
   virtual int32_t Reset(PP_CompletionCallback callback) = 0;
-  virtual int32_t Destroy(PP_CompletionCallback callback) = 0;
+  virtual void Destroy() = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_VIDEO_DECODER_API_H_