Detect change on the intersection of video and viewport.

media/remoting/remoting_renderer_controller.h

Index: media/remoting/remoting_renderer_controller.h
diff --git a/media/remoting/remoting_renderer_controller.h b/media/remoting/remoting_renderer_controller.h
index 9c98af12b555441c1ade86ff34291b321c7a8076..b2b3eaf69d0229ba25f5773a40440d8f7999294d 100644
--- a/media/remoting/remoting_renderer_controller.h
+++ b/media/remoting/remoting_renderer_controller.h
@@ -35,6 +35,8 @@ class RemotingRendererController final : public RemotingSourceImpl::Client,
   // MediaObserver implementations.
   void OnEnteredFullscreen() override;
   void OnExitedFullscreen() override;
+  void OnStablyFilledMostViewportChanged(
+      bool is_mostly_filling_viewport) override;
   void OnSetCdm(CdmContext* cdm_context) override;
   void OnMetadataChanged(const PipelineMetadata& metadata) override;
 
@@ -103,6 +105,9 @@ class RemotingRendererController final : public RemotingSourceImpl::Client,
   VideoDecoderConfig video_decoder_config_;
   AudioDecoderConfig audio_decoder_config_;
 
+  // Indicates whether video fills most of the viewport.
+  bool is_mostly_filling_viewport_ = false;
+
   // The callback to switch the media renderer.
   base::Closure switch_renderer_cb_;