--- a/dom/media/MediaStreamGraph.cpp
+++ b/dom/media/MediaStreamGraph.cpp
@@ -1908,16 +1908,22 @@ MediaStream::GraphTimeToStreamTimeWithBl
 
 void
 MediaStream::FinishOnGraphThread()
 {
   GraphImpl()->FinishStream(this);
 }
 
 StreamBuffer::Track*
+MediaStream::FindTrack(TrackID aID)
+{
+  return mBuffer.FindTrack(aID);
+}
+
+StreamBuffer::Track*
 MediaStream::EnsureTrack(TrackID aTrackId)
 {
   StreamBuffer::Track* track = mBuffer.FindTrack(aTrackId);
   if (!track) {
     nsAutoPtr<MediaSegment> segment(new AudioSegment());
     for (uint32_t j = 0; j < mListeners.Length(); ++j) {
       MediaStreamListener* l = mListeners[j];
       l->NotifyQueuedTrackChanges(Graph(), aTrackId, 0,
@@ -2537,22 +2543,16 @@ SourceMediaStream::FinishAddTracks()
 {
   MutexAutoLock lock(mMutex);
   mUpdateTracks.AppendElements(Move(mPendingTracks));
   if (GraphImpl()) {
     GraphImpl()->EnsureNextIteration();
   }
 }
 
-StreamBuffer::Track*
-SourceMediaStream::FindTrack(TrackID aID)
-{
-  return mBuffer.FindTrack(aID);
-}
-
 void
 SourceMediaStream::ResampleAudioToGraphSampleRate(TrackData* aTrackData, MediaSegment* aSegment)
 {
   if (aSegment->GetType() != MediaSegment::AUDIO ||
       aTrackData->mInputRate == GraphImpl()->GraphRate()) {
     return;
   }
   AudioSegment* segment = static_cast<AudioSegment*>(aSegment);

--- a/dom/media/MediaStreamGraph.h
+++ b/dom/media/MediaStreamGraph.h
@@ -753,16 +753,21 @@ public:
    */
   GraphTime StreamTimeToGraphTime(StreamTime aTime);
 
   bool IsFinishedOnGraphThread() { return mFinished; }
   void FinishOnGraphThread();
 
   bool HasCurrentData() { return mHasCurrentData; }
 
+  /**
+   * Find track by track id.
+   */
+  StreamBuffer::Track* FindTrack(TrackID aID);
+
   StreamBuffer::Track* EnsureTrack(TrackID aTrack);
 
   virtual void ApplyTrackDisabling(TrackID aTrackID, MediaSegment* aSegment, MediaSegment* aRawSegment = nullptr);
 
   DOMMediaStream* GetWrapper()
   {
     NS_ASSERTION(NS_IsMainThread(), "Only use DOMMediaStream on main thread");
     return mWrapper;
@@ -996,21 +1001,16 @@ public:
 
   /**
    * Call after a series of AddTrack or AddAudioTrack calls to implement
    * any pending track adds.
    */
   void FinishAddTracks();
 
   /**
-   * Find track by track id.
-   */
-  StreamBuffer::Track* FindTrack(TrackID aID);
-
-  /**
    * Append media data to a track. Ownership of aSegment remains with the caller,
    * but aSegment is emptied.
    * Returns false if the data was not appended because no such track exists
    * or the stream was already finished.
    */
   bool AppendToTrack(TrackID aID, MediaSegment* aSegment, MediaSegment *aRawSegment = nullptr);
   /**
    * Get the stream time of the end of the data that has been appended so far.