Bug 1081819 - Handle InMutedCycle() in TrackUnionStream::ProcessInput. r=roc,padenot

dom/media/TrackUnionStream.cpp

@@ -272,6 +272,8 @@ TrackUnionStream::TrackUnionStream(DOMMediaStream* aWrapper) :
         segment->AppendNullData(ticks);
         STREAM_LOG(PR_LOG_DEBUG+1, ("TrackUnionStream %p appending %lld ticks of null data to track %d",
                    this, (long long)ticks, outputTrack->GetID()));
+      } else if (InMutedCycle()) {
+        segment->AppendNullData(ticks);
       } else {
         MOZ_ASSERT(outputTrack->GetEnd() == GraphTimeToStreamTime(interval.mStart),
                    "Samples missing");