Notify on console when play fails

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index f66f59c4422ba466b0ee4f8c44bcdb3692db78c2..ca5f073d20253e8a8c2617fe00db7cfcb3f5f66c 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -59,6 +59,7 @@
 #include "core/html/track/TextTrackList.h"
 #include "core/html/track/VideoTrack.h"
 #include "core/html/track/VideoTrackList.h"
+#include "core/inspector/ConsoleMessage.h"
 #include "core/layout/LayoutVideo.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/compositing/DeprecatedPaintLayerCompositor.h"
@@ -1914,8 +1915,16 @@ void HTMLMediaElement::play()
 
     if (!UserGestureIndicator::processingUserGesture()) {
         autoplayMediaEncountered();
-        if (m_userGestureRequiredForPlay)
+        if (m_userGestureRequiredForPlay) {
+            // prevent autoplay, and make it known

[jww, 2015/06/03 22:58:51]

Please remove this comment, as it is unnecessary.

[keenanb, 2015/06/04 00:07:13]

Done.

+            String messageString = ExceptionMessages::failedToExecute(
+                "play",

[jww, 2015/06/03 22:58:51]

Please put these arguments on one line.

[keenanb, 2015/06/04 00:07:13]

Done.

+                "MediaElement",
+                "the API can be initiated only by the user.");

[jww, 2015/06/03 22:58:51]

Please make this message match the message in the Fullscreen API, so it should
read: 
   API can only be initiated by a user gesture.

[keenanb, 2015/06/04 00:07:13]

Done.

+            document().executionContext()->addConsoleMessage(
+                ConsoleMessage::create(JSMessageSource, WarningMessageLevel, messageString));

[jww, 2015/06/03 22:58:51]

Please put this argument on the previous line.

[keenanb, 2015/06/04 00:07:12]

Done.

             return;
+        }
     } else if (m_userGestureRequiredForPlay) {
         if (m_autoplayMediaCounted)
             recordAutoplayMetric(AutoplayManualStart);