Bug 1211443 - Drop scheduled update if decoder initialization isn't done yet. r=jya

dom/media/MediaFormatReader.cpp

@@ -1047,7 +1047,7 @@ MediaFormatReader::Update(TrackType aTrack)
 {
   MOZ_ASSERT(OnTaskQueue());
 
-  if (mShutdown || !mInitDone) {
+  if (mShutdown) {
     return;
   }
 
@@ -1058,6 +1058,10 @@ MediaFormatReader::Update(TrackType aTrack)
   auto& decoder = GetDecoderData(aTrack);
   decoder.mUpdateScheduled = false;
 
+  if (!mInitDone) {
+    return;
+  }
+
   if (UpdateReceivedNewData(aTrack)) {
     LOGV("Nothing more to do");
     return;