Bug 1065827 - Invalidate video frame container during FirstFrameLoaded. r=jwwang

dom/media/MediaDecoder.cpp

@@ -741,6 +741,7 @@ void MediaDecoder::FirstFrameLoaded(MediaInfo* aInfo)
   mInfo = aInfo;
 
   if (mOwner) {
+    Invalidate();
     mOwner->FirstFrameLoaded();
   }