Bug 1554699 - Don't fire "timeupdate" in PlayInternal as it's against spec. r=jya,alwu

Bug 1279865 introduced this under the premise of
"Run TimeMarchesOn() at the beginning of play.", but it did a bit too much.

This makes us spec compliant for this particular case again.

Differential Revision: https://phabricator.services.mozilla.com/D33650

dom/html/HTMLMediaElement.cpp

@@ -3800,7 +3800,6 @@ void HTMLMediaElement::PlayInternal(bool aHandlingUserInput) {
         break;
       case HAVE_FUTURE_DATA:
       case HAVE_ENOUGH_DATA:
-        FireTimeUpdate(false);
         NotifyAboutPlaying();
         break;
     }