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

ppapi/shared_impl/media_stream_frame_buffer.cc

Index: ppapi/shared_impl/media_stream_frame_buffer.cc
diff --git a/ppapi/shared_impl/media_stream_frame_buffer.cc b/ppapi/shared_impl/media_stream_frame_buffer.cc
index 624883039ecb881504d6b9aa33b0e6adbe6538cb..41586aa445019bdca422b7bd75b8e4b1fe7e1495 100644
--- a/ppapi/shared_impl/media_stream_frame_buffer.cc
+++ b/ppapi/shared_impl/media_stream_frame_buffer.cc
@@ -29,6 +29,7 @@ bool MediaStreamFrameBuffer::SetFrames(
     int32_t frame_size,
     scoped_ptr<base::SharedMemory> shm,
     bool enqueue_all_frames) {
+  base::AutoLock lock(mutex_);
   DCHECK(shm);
   DCHECK(!shm_);
   DCHECK_GT(number_of_frames, 0);
@@ -54,6 +55,7 @@ bool MediaStreamFrameBuffer::SetFrames(
 }
 
 int32_t MediaStreamFrameBuffer::DequeueFrame() {
+  base::AutoLock lock(mutex_);
   if (frame_queue_.empty())
     return PP_ERROR_FAILED;
   int32_t frame = frame_queue_.front();
@@ -64,12 +66,16 @@ int32_t MediaStreamFrameBuffer::DequeueFrame() {
 void MediaStreamFrameBuffer::EnqueueFrame(int32_t index) {
   DCHECK_GE(index, 0);
   DCHECK_LT(index, number_of_frames_);
-  frame_queue_.push_back(index);
+  {
+    base::AutoLock lock(mutex_);
+    frame_queue_.push_back(index);
+  }
   delegate_->OnNewFrameEnqueued();
 }
 
 MediaStreamFrame* MediaStreamFrameBuffer::GetFramePointer(
     int32_t index) {
+  base::AutoLock lock(mutex_);
   DCHECK_GE(index, 0);
   DCHECK_LT(index, number_of_frames_);
   return frames_[index];