Always show "exit fullscreen" button.

Source/core/html/shadow/MediaControls.cpp

 /*
  * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 166 matching lines @@
     m_timeline->setPosition(mediaElement().currentTime());
 
     if (!mediaElement().hasAudio())
         m_volumeSlider->hide();
     else
         m_volumeSlider->show();
     updateVolume();
 
     refreshClosedCaptionsButtonVisibility();
 
-    if (mediaElement().hasVideo() && fullscreenIsSupported(document()))
+    if ((mediaElement().hasVideo() && fullscreenIsSupported(document()))
+        || mediaElement().isFullscreen())

[xhwang, 2015/06/23 20:22:01]

Maybe add some comment here. Otherwise it makes people wonder how we get into
the fullscreen mode in the first place.

[eae, 2015/06/23 20:30:45]

Seconded.

[liberato (no reviews please), 2015/06/23 20:37:41]

third-ed.  i had additional logic that i removed, and deleted the comment along
with it.  oops.

         m_fullScreenButton->show();
     else
         m_fullScreenButton->hide();
 
     refreshCastButtonVisibility();
     makeOpaque();
 }
 
 LayoutObject* MediaControls::layoutObjectForTextTrackLayout()
 {
@@ skipping 335 matching lines @@
     visitor->trace(m_toggleClosedCaptionsButton);
     visitor->trace(m_fullScreenButton);
     visitor->trace(m_durationDisplay);
     visitor->trace(m_enclosure);
     visitor->trace(m_castButton);
     visitor->trace(m_overlayCastButton);
     HTMLDivElement::trace(visitor);
 }
 
 }