Monitor 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..35d505fe8226c2f3b5ae2134559d52f2ce4e1c34 100644
--- a/media/remoting/remoting_renderer_controller.h
+++ b/media/remoting/remoting_renderer_controller.h
@@ -7,6 +7,7 @@
 
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
+#include "base/timer/timer.h"
 #include "media/base/media_observer.h"
 #include "media/remoting/remoting_source_impl.h"
 
@@ -35,6 +36,8 @@ class RemotingRendererController final : public RemotingSourceImpl::Client,
   // MediaObserver implementations.
   void OnEnteredFullscreen() override;
   void OnExitedFullscreen() override;
+  void OnVideoViewportIntersectionChanged(
+      const ViewportIntersectionInfo& info) override;
   void OnSetCdm(CdmContext* cdm_context) override;
   void OnMetadataChanged(const PipelineMetadata& metadata) override;
 
@@ -90,6 +93,10 @@ class RemotingRendererController final : public RemotingSourceImpl::Client,
   // necessary.
   void UpdateAndMaybeSwitch();
 
+  // Callback from |viewport_fill_debouncer_timer_| when video keeps covering
+  // most of the viewport for a certain time.
+  void OnViewportMostlyFilledAndUnchanging();
+
   // Indicates whether this media element or its ancestor is in full screen.
   bool is_fullscreen_ = false;
 
@@ -103,6 +110,13 @@ class RemotingRendererController final : public RemotingSourceImpl::Client,
   VideoDecoderConfig video_decoder_config_;
   AudioDecoderConfig audio_decoder_config_;
 
+  // Indicates whether video covers most of the viewport.
+  bool is_mostly_filling_viewport_ = false;
+
+  // Video/Viewport ratio meeting/exceeding the threshold should hold steady for
+  // a certain time before attempting to start remoting.
+  base::OneShotTimer viewport_fill_debouncer_timer_;
+
   // The callback to switch the media renderer.
   base::Closure switch_renderer_cb_;