[PPAPI] Pepper MediaStream API audio track implementation and example.

ppapi/thunk/ppb_video_frame_api.h

 // Copyright 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 PPAPI_THUNK_PPB_VIDEO_FRAME_API_H_
 #define PPAPI_THUNK_PPB_VIDEO_FRAME_API_H_
 
 #include "ppapi/c/ppb_video_frame.h"
 #include "ppapi/thunk/ppapi_thunk_export.h"
 
 namespace ppapi {
 
 union MediaStreamFrame;
 
 namespace thunk {
 
 class PPAPI_THUNK_EXPORT PPB_VideoFrame_API {
  public:
   virtual ~PPB_VideoFrame_API() {}
   virtual PP_TimeDelta GetTimestamp() = 0;
   virtual void SetTimestamp(PP_TimeDelta timestamp) = 0;
   virtual PP_VideoFrame_Format GetFormat() = 0;
   virtual PP_Bool GetSize(PP_Size* size) = 0;
   virtual void* GetDataBuffer() = 0;
   virtual uint32_t GetDataBufferSize() = 0;
 
-  // Private APIs:
+  // Methods used by Pepper internal implementation only.
   virtual MediaStreamFrame* GetFrameBuffer() = 0;
   virtual int32_t GetFrameBufferIndex() = 0;
   virtual void Invalidate() = 0;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_PPB_VIDEO_FRAME_API_H_