Bug 996331 - Remove TextTrack.oncuechange. r=cpearce,smaug

This event isn't currently implemented. Removing it from
the DOM interface provides a way for authors to detect
that it cannot be expected to work.

dom/webidl/TextTrack.webidl

@@ -39,7 +39,7 @@ interface TextTrack : EventTarget {
   [Throws]
   void removeCue(VTTCue cue);
 
-           attribute EventHandler oncuechange;
+           //(Not implemented)attribute EventHandler oncuechange;
 };
 
 // Mozilla Extensions