Post GpuMemoryBufferVideoFramePool deletion on media thread

content/renderer/media/media_stream_video_renderer_sink.cc

Index: content/renderer/media/media_stream_video_renderer_sink.cc
diff --git a/content/renderer/media/media_stream_video_renderer_sink.cc b/content/renderer/media/media_stream_video_renderer_sink.cc
index 709f9d51d8f11139c35d11b2eb15235c36a52848..6fff1d9c81f58097bac9f37b1e307f3f24bb1c79 100644
--- a/content/renderer/media/media_stream_video_renderer_sink.cc
+++ b/content/renderer/media/media_stream_video_renderer_sink.cc
@@ -40,6 +40,10 @@ MediaStreamVideoRendererSink::MediaStreamVideoRendererSink(
 }
 
 MediaStreamVideoRendererSink::~MediaStreamVideoRendererSink() {
+  if (gpu_memory_buffer_pool_) {
+    media_task_runner_->DeleteSoon(FROM_HERE,
+                                   gpu_memory_buffer_pool_.release());
+  }
 }
 
 void MediaStreamVideoRendererSink::Start() {
@@ -109,6 +113,9 @@ void MediaStreamVideoRendererSink::OnVideoFrame(
     return;
   }
 
+  //  |gpu_memory_buffer_pool_| deletion is going to be posted to
+  //  |media_task_runner_|. base::Unretained() usage is fine since

[mcasas, 2016/02/10 23:24:02]

Unretained? I see |gpu_memory_buffer_pool_| is only used
in |media_task_runner_|, so why not adding to the pool a 
WeakPtrFactory, and in l.111, instead of testing for 
|!gpu_memory_buffer_pool_|, add a 

bool ShouldUseGpuMemoryBuffers() {
  return gpu_factories &&
gpu_factories->ShouldUseGpuMemoryBuffersForVideoFrames();
}

and use it in l.35, 43 and 111 ?

[emircan, 2016/02/11 00:13:19]

I added WeakPtrFactory and GetWeakPtr() calls in PS#3

However, it looks like you and dcastagna@ have very strong opinions about
Unretained vs. WeakPtr usage. I will leave this discussion up to you, and will
move on with the one you agree on.

Personally, I think Unretained and WeakPtr both provide the same functionality
in this case, as dtor deletes the scoped_ptr() and there wouldn't be any more
tasks. Also, I understand that WeakPtr&DeleteSoon has been used in Chrome as a
pattern. I think WeakPtr would have the edge in this discussion, just in case
GpuMemoryBufferVideoFramePool calls invalidatePtrs() in case of a loss.

+  //  |gpu_memory_buffer_pool_| outlives the task.
   media_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(