PPAPI: Make blocking completion callbacks work.

ppapi/thunk/ppb_video_decoder_api.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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_THUNK_VIDEO_DECODER_API_H_
 #define PPAPI_THUNK_VIDEO_DECODER_API_H_
 
+#include "base/memory/ref_counted.h"
 #include "ppapi/c/dev/ppb_video_decoder_dev.h"
 
 namespace ppapi {
+
+class TrackedCallback;
+
 namespace thunk {
 
 class PPB_VideoDecoder_API {
  public:
   virtual ~PPB_VideoDecoder_API() {}
 
   virtual int32_t Decode(const PP_VideoBitstreamBuffer_Dev* bitstream_buffer,
-                         PP_CompletionCallback callback) = 0;
+                         scoped_refptr<TrackedCallback> callback) = 0;
   virtual void AssignPictureBuffers(uint32_t no_of_buffers,
                                     const PP_PictureBuffer_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 Flush(scoped_refptr<TrackedCallback> callback) = 0;
+  virtual int32_t Reset(scoped_refptr<TrackedCallback> callback) = 0;
   virtual void Destroy() = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_VIDEO_DECODER_API_H_