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

media/blink/buffered_resource_loader.h

Index: media/blink/buffered_resource_loader.h
diff --git a/media/blink/buffered_resource_loader.h b/media/blink/buffered_resource_loader.h
index a458b4dd89d1c1db545a1146c666c18e96f308b7..b4dec9a63c9f4c5b2274308405750ad048954a19 100644
--- a/media/blink/buffered_resource_loader.h
+++ b/media/blink/buffered_resource_loader.h
@@ -210,6 +210,9 @@ class MEDIA_EXPORT BufferedResourceLoader
   // a Service Worker it is empty.
   const GURL response_original_url() const { return response_original_url_; }
 
+  // Returns an estimate of the amount of memory owned by the resource loader.
+  int64_t GetMemoryUsage() const;
+
  private:
   friend class BufferedDataSourceTest;
   friend class BufferedResourceLoaderTest;