Notify WebMediaPlayer when its ancestor enters/exists fullscreen.

media/blink/webmediaplayer_impl.h

Index: media/blink/webmediaplayer_impl.h
diff --git a/media/blink/webmediaplayer_impl.h b/media/blink/webmediaplayer_impl.h
index 8fcae51c904b86ce45a47e463d2ef69341a3ce10..6d724048f1a9b4e03cf665b7c3fbceebe2c29b35 100644
--- a/media/blink/webmediaplayer_impl.h
+++ b/media/blink/webmediaplayer_impl.h
@@ -181,6 +181,9 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   bool supportsOverlayFullscreenVideo() override;
   void enteredFullscreen() override;
   void exitedFullscreen() override;
+  void enterFullWindow() override;
+  bool isFullWindow() override;
+  void exitFullWindow() override;
 
   // WebMediaPlayerDelegate::Observer implementation.
   void OnHidden() override;
@@ -554,6 +557,10 @@ class MEDIA_BLINK_EXPORT WebMediaPlayerImpl
   int underflow_count_;
   std::unique_ptr<base::ElapsedTimer> underflow_timer_;
 
+  // Whether the video covers most of the window when its ancestor enters full
+  // screen.
+  bool is_full_window_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };