Have HTMLMediaElement::play() return a Promise.

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

Index: third_party/WebKit/Source/core/html/shadow/MediaControls.cpp
diff --git a/third_party/WebKit/Source/core/html/shadow/MediaControls.cpp b/third_party/WebKit/Source/core/html/shadow/MediaControls.cpp
index e78e237e5fd378fe3dd1430bdd455906ad4f9cad..26ec49c39eb2416279ba5dae28bdc1399bcf610a 100644
--- a/third_party/WebKit/Source/core/html/shadow/MediaControls.cpp
+++ b/third_party/WebKit/Source/core/html/shadow/MediaControls.cpp
@@ -383,11 +383,12 @@ void MediaControls::beginScrubbing()
 
 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()