Provide a WebContents API to discover the playback of a fullscreen video.

media/blink/webmediaplayer_delegate.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BLINK_WEBMEDIAPLAYER_DELEGATE_H_
 #define MEDIA_BLINK_WEBMEDIAPLAYER_DELEGATE_H_
 
 namespace blink {
 class WebMediaPlayer;
 }
@@ skipping 98 matching lines @@
   // without an additional idle timeout.
   // TODO(sandersd): This exists only to support WMPI's didLoadingProgress()
   // workaround. A better option may be to take a 'minimum idle' duration in
   // SetIdle().
   virtual void ClearStaleFlag(int player_id) = 0;
 
   // Returns |true| if the player is stale; that is that OnIdleTimeout() was
   // called and returned |true|.
   virtual bool IsStale(int player_id) = 0;
 
+  // Notifies the delegate that the player has entered fullscreen. This does not
+  // differentiate native controls fullscreen and custom controls fullscreen.

[liberato (no reviews please), 2017/02/22 18:28:20]

i like these new semantics better.  might want to include 'Effectively' here
too, just so that it matches the observer.

[mlamouri (slow - plz ping), 2017/02/22 19:23:26]

I agree. Updated :)

+  virtual void SetIsFullscreen(int player_id, bool is_fullscreen) = 0;
+
  protected:
   WebMediaPlayerDelegate() = default;
   virtual ~WebMediaPlayerDelegate() = default;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_WEBMEDIAPLAYER_DELEGATE_H_