Add methods for telling V8 how much memory audio/video is using.

media/renderers/video_renderer_impl.h

Index: media/renderers/video_renderer_impl.h
diff --git a/media/renderers/video_renderer_impl.h b/media/renderers/video_renderer_impl.h
index 17f7cfce4aaa4ffe1a116c18df7bd4893cecc308..75a8d03b3e154817458cfdacd13bbb4373b502af 100644
--- a/media/renderers/video_renderer_impl.h
+++ b/media/renderers/video_renderer_impl.h
@@ -256,6 +256,10 @@ class MEDIA_EXPORT VideoRendererImpl
   bool render_first_frame_and_stop_;
   bool posted_maybe_stop_after_first_paint_;
 
+  // Memory usage of |algorithm_| recorded during the last UpdateStats_Locked()
+  // call.
+  int64_t last_video_memory_usage_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<VideoRendererImpl> weak_factory_;