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

ppapi/proxy/media_stream_video_track_resource.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 "ppapi/proxy/media_stream_video_track_resource.h"
 
 #include "base/logging.h"
 #include "ppapi/proxy/video_frame_resource.h"
 #include "ppapi/shared_impl/media_stream_frame.h"
 #include "ppapi/shared_impl/var.h"
@@ skipping 36 matching lines @@
 
 int32_t MediaStreamVideoTrackResource::GetFrame(
     PP_Resource* frame,
     scoped_refptr<TrackedCallback> callback) {
   if (has_ended())
     return PP_ERROR_FAILED;
 
   if (TrackedCallback::IsPending(get_frame_callback_))
     return PP_ERROR_INPROGRESS;
 
-  *frame = GetVideoFrame();
+  *frame = GetVideoFrame(-1);
   if (*frame)
     return PP_OK;
 
   get_frame_output_ = frame;
   get_frame_callback_ = callback;
   return PP_OK_COMPLETIONPENDING;
 }
 
 int32_t MediaStreamVideoTrackResource::RecycleFrame(PP_Resource frame) {
   FrameMap::iterator it = frames_.find(frame);
@@ skipping 21 matching lines @@
     *get_frame_output_ = 0;
     get_frame_callback_->PostAbort();
     get_frame_callback_ = NULL;
     get_frame_output_ = 0;
   }
 
   ReleaseFrames();
   MediaStreamTrackResourceBase::CloseInternal();
 }
 
-void MediaStreamVideoTrackResource::OnNewFrameEnqueued() {
-  if (TrackedCallback::IsPending(get_frame_callback_)) {
-    *get_frame_output_ = GetVideoFrame();
-    get_frame_output_ = NULL;
-    scoped_refptr<TrackedCallback> callback;
-    callback.swap(get_frame_callback_);
-    callback->Run(PP_OK);
-  }
+bool MediaStreamVideoTrackResource::OnNewFramePreEnqueued(int32_t index) {
+  if (!TrackedCallback::IsPending(get_frame_callback_))
+    return false;
+
+  *get_frame_output_ = GetVideoFrame(index);
+  get_frame_output_ = NULL;
+  scoped_refptr<TrackedCallback> callback;
+  callback.swap(get_frame_callback_);
+  callback->Run(PP_OK);
+  return true;
 }
 
-PP_Resource MediaStreamVideoTrackResource::GetVideoFrame() {
-  int32_t index = frame_buffer()->DequeueFrame();
-  if (index < 0)
-    return 0;
+PP_Resource MediaStreamVideoTrackResource::GetVideoFrame(int32_t index) {
+  if (index < 0) {
+    index = frame_buffer()->DequeueFrame();
+    if (index < 0)
+      return 0;
+  }
   MediaStreamFrame* frame = frame_buffer()->GetFramePointer(index);
+  DCHECK(frame);
   scoped_refptr<VideoFrameResource> resource =
       new VideoFrameResource(pp_instance(), index, frame);
   // Add |pp_resource()| and |resource| into |frames_|.
   // |frames_| uses scoped_ptr<> to hold a ref of |resource|. It keeps the
   // resource alive.
   frames_.insert(FrameMap::value_type(resource->pp_resource(), resource));
   return resource->GetReference();
 }
 
 void MediaStreamVideoTrackResource::ReleaseFrames() {
   FrameMap::iterator it = frames_.begin();
   while (it != frames_.end()) {
     // Just invalidate and release VideoFrameResorce, but keep PP_Resource.
     // So plugin can still use |RecycleFrame()|.
     it->second->Invalidate();
     it->second = NULL;
   }
 }
 
 }  // namespace proxy
 }  // namespace ppapi