Post GpuMemoryBufferVideoFramePool deletion on media thread

content/renderer/media/media_stream_video_renderer_sink_unittest.cc

Index: content/renderer/media/media_stream_video_renderer_sink_unittest.cc
diff --git a/content/renderer/media/media_stream_video_renderer_sink_unittest.cc b/content/renderer/media/media_stream_video_renderer_sink_unittest.cc
index 9b3b35a05e71bf5a19e91bf7704bd3c9b6816a9e..32b23e39ab5bfc033eb8746a236fa552e2f7a688 100644
--- a/content/renderer/media/media_stream_video_renderer_sink_unittest.cc
+++ b/content/renderer/media/media_stream_video_renderer_sink_unittest.cc
@@ -59,6 +59,9 @@ class MediaStreamVideoRendererSinkTest : public testing::Test {
     media_stream_video_renderer_sink_ = nullptr;
     registry_.reset();
     blink::WebHeap::collectAllGarbageForTesting();
+
+    // Let the message loop run to finish destroying the pool.
+    base::RunLoop().RunUntilIdle();
   }
 
   MOCK_METHOD1(RepaintCallback, void(const scoped_refptr<media::VideoFrame>&));