Have HTMLMediaElement::play() return a Promise.

third_party/WebKit/Source/core/html/shadow/MediaControlElements.cpp

 /*
  * Copyright (C) 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 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.
@@ skipping 297 matching lines @@
     RefPtrWillBeRawPtr<MediaControlOverlayPlayButtonElement> button = adoptRefWillBeNoop(new MediaControlOverlayPlayButtonElement(mediaControls));
     button->ensureUserAgentShadowRoot();
     button->setType(InputTypeNames::button);
     button->setShadowPseudoId(AtomicString("-webkit-media-controls-overlay-play-button", AtomicString::ConstructFromLiteral));
     return button.release();
 }
 
 void MediaControlOverlayPlayButtonElement::defaultEventHandler(Event* event)
 {
     if (event->type() == EventTypeNames::click && mediaElement().paused()) {
-        mediaElement().play();
+        mediaElement().playInternal();

[philipj_slow, 2016/02/02 09:56:33]

Also potentially risky.

[mlamouri (slow - plz ping), 2016/02/03 19:28:58]

Reverted.

         updateDisplayType();
         event->setDefaultHandled();
     }
 }
 
 void MediaControlOverlayPlayButtonElement::updateDisplayType()
 {
     setIsWanted(mediaElement().shouldShowControls() && mediaElement().paused());
 }
 
@@ skipping 319 matching lines @@
 }
 
 PassRefPtrWillBeRawPtr<MediaControlCurrentTimeDisplayElement> MediaControlCurrentTimeDisplayElement::create(MediaControls& mediaControls)
 {
     RefPtrWillBeRawPtr<MediaControlCurrentTimeDisplayElement> element = adoptRefWillBeNoop(new MediaControlCurrentTimeDisplayElement(mediaControls));
     element->setShadowPseudoId(AtomicString("-webkit-media-controls-current-time-display", AtomicString::ConstructFromLiteral));
     return element.release();
 }
 
 } // namespace blink