Bug 1276495: Don't reset audio promises for video only seek. r=jwwang,jya

ResetDecode was disconnecting mAudioDataRequest when seeking video
only. This means that, if a RequestAudioData() was outstanding,
mAudioDataRequest and MFR.mAudio.mHasPromise would become out-of-sync.

MozReview-Commit-ID: EaS5NERsxpt

dom/media/MediaDecoderReaderWrapper.cpp

@@ -397,9 +397,11 @@ MediaDecoderReaderWrapper::ResetDecode(TargetQueues aQueues)
 {
   MOZ_ASSERT(mOwnerThread->IsCurrentThreadIn());
 
-  mAudioDataRequest.DisconnectIfExists();
+  if (aQueues == MediaDecoderReader::AUDIO_VIDEO) {
+    mAudioDataRequest.DisconnectIfExists();
+    mAudioWaitRequest.DisconnectIfExists();
+  }
   mVideoDataRequest.DisconnectIfExists();
-  mAudioWaitRequest.DisconnectIfExists();
   mVideoWaitRequest.DisconnectIfExists();
 
   nsCOMPtr<nsIRunnable> r =