Bug 1303554 - part1 : notify start-playing after having enough data. r=baku

Regression by bug1262053 because of removing the current playing checking.
It would cause that the media control on Fennec shows too early and some media
elements would also generate the media control even it doens't have available
source.

Therefore, I think we still need to add this checking back.

MozReview-Commit-ID: 1m1ywmLmpSe

dom/html/HTMLMediaElement.cpp

@@ -5755,6 +5755,11 @@ HTMLMediaElement::IsPlayingThroughTheAudioChannel() const
     return true;
   }
 
+  // If we are actually playing...
+  if (IsCurrentlyPlaying()) {
+    return true;
+  }
+
   // If we are seeking, we consider it as playing
   if (mPlayingThroughTheAudioChannelBeforeSeek) {
     return true;
@@ -5765,7 +5770,7 @@ HTMLMediaElement::IsPlayingThroughTheAudioChannel() const
     return true;
   }
 
-  return true;
+  return false;
 }
 
 void