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

content/renderer/pepper/pepper_media_stream_track_host_base.cc

 // 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.
 
 #include "content/renderer/pepper/pepper_media_stream_track_host_base.h"
 
 #include "base/logging.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/public/renderer/renderer_ppapi_host.h"
 #include "ppapi/c/pp_errors.h"
@@ skipping 21 matching lines @@
 }
 
 bool PepperMediaStreamTrackHostBase::InitFrames(int32_t number_of_frames,
                                                 int32_t frame_size) {
   DCHECK_GT(number_of_frames, 0);
   DCHECK_GT(frame_size,
             static_cast<int32_t>(sizeof(ppapi::MediaStreamFrame::Header)));
   // Make each frame 4 byte aligned.
   frame_size = (frame_size + 3) & ~0x3;
 
+  // TODO(penghuang): |HostAllocateSharedMemoryBuffer| uses sync IPC. We should
+  // avoid it.
   int32_t size = number_of_frames * frame_size;
   content::RenderThread* render_thread = content::RenderThread::Get();
   scoped_ptr<base::SharedMemory> shm(
       render_thread->HostAllocateSharedMemoryBuffer(size).Pass());
   if (!shm)
     return false;
 
   base::SharedMemoryHandle shm_handle = shm->handle();
   if (!frame_buffer_.SetFrames(number_of_frames, frame_size, shm.Pass(), true))
     return false;
@@ skipping 41 matching lines @@
   return PP_OK;
 }
 
 int32_t PepperMediaStreamTrackHostBase::OnHostMsgClose(
     HostMessageContext* context) {
   OnClose();
   return PP_OK;
 }
 
 }  // namespace content