[Video] Reset new processed frame callback on the compositor thread.

media/blink/video_frame_compositor.cc

Index: media/blink/video_frame_compositor.cc
diff --git a/media/blink/video_frame_compositor.cc b/media/blink/video_frame_compositor.cc
index ec2034240c4f13b5ea188176159c35b8774e08c1..5288716244a2cc2b48315a7b479aa0b98d430f6d 100644
--- a/media/blink/video_frame_compositor.cc
+++ b/media/blink/video_frame_compositor.cc
@@ -63,6 +63,7 @@ void VideoFrameCompositor::OnRendererStateUpdate(bool new_state) {
   if (rendering_) {
     auto_open_close_->Begin();
   } else {
+    new_processed_frame_cb_.Reset();
     auto_open_close_->End();
   }
 
@@ -139,7 +140,6 @@ void VideoFrameCompositor::Stop() {
   compositor_task_runner_->PostTask(
       FROM_HERE, base::Bind(&VideoFrameCompositor::OnRendererStateUpdate,
                             base::Unretained(this), false));
-  new_processed_frame_cb_.Reset();
 }
 
 void VideoFrameCompositor::PaintSingleFrame(