Bug 1182985: Drain decoder when changing resolution. r=cpearce

dom/media/MediaFormatReader.cpp

@@ -875,6 +875,17 @@ MediaFormatReader::DecodeDemuxedSamples(TrackType aTrack,
         return;
       }
 
+      if (decoder.mNextStreamSourceID.isNothing() ||
+          decoder.mNextStreamSourceID.ref() != info->GetID()) {
+        LOG("%s stream id has changed from:%d to:%d, draining decoder.",
+            TrackTypeToStr(aTrack), decoder.mLastStreamSourceID,
+            info->GetID());
+        decoder.mNeedDraining = true;
+        decoder.mNextStreamSourceID = Some(info->GetID());
+        DrainDecoder(aTrack);
+        return;
+      }
+
       LOG("%s stream id has changed from:%d to:%d, recreating decoder.",
           TrackTypeToStr(aTrack), decoder.mLastStreamSourceID,
           info->GetID());

dom/media/MediaFormatReader.h

@@ -285,12 +285,14 @@ private:
       mNumSamplesInput = 0;
       mNumSamplesOutput = 0;
       mSizeOfQueue = 0;
+      mNextStreamSourceID.reset();
     }
 
     // Used by the MDSM for logging purposes.
     Atomic<size_t> mSizeOfQueue;
     // Sample format monitoring.
     uint32_t mLastStreamSourceID;
+    Maybe<uint32_t> mNextStreamSourceID;
     media::TimeIntervals mTimeRanges;
     nsRefPtr<SharedTrackInfo> mInfo;
   };