Have HTMLMediaElement::play() return a Promise.

third_party/WebKit/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 365 matching lines @@
 void MediaControls::beginScrubbing()
 {
     if (!mediaElement().paused()) {
         m_isPausedForScrubbing = true;
         mediaElement().pause();
     }
 }
 
 void MediaControls::endScrubbing()
 {
-    if (m_isPausedForScrubbing) {
-        m_isPausedForScrubbing = false;
-        if (mediaElement().paused())
-            mediaElement().play();
-    }
+    if (!m_isPausedForScrubbing)
+        return;
+
+    m_isPausedForScrubbing = false;
+    if (mediaElement().paused())
+        mediaElement().playInternal();

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

Hmm, this case need not require a user gesture, but it'd also be bad if it could
bypass the new m_error check.

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

Fixed.

 }
 
 void MediaControls::updateCurrentTimeDisplay()
 {
     double now = mediaElement().currentTime();
     double duration = mediaElement().duration();
 
     // After seek, hide duration display and show current time.
     if (!RuntimeEnabledFeatures::newMediaPlaybackUiEnabled() && now > 0) {
         BatchedControlUpdate batch(this);
@@ skipping 348 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);
 }
 
 } // namespace blink