Bug 1401147 - part1 : empty track buffer content upon detach. r=jya

After detached the source buffer, we would reset all its resource and shutdown
demuxer.

MozReview-Commit-ID: 7xEJ7q00aeF

--HG--
extra : rebase_source : c80ebb2e9ed6c9d3a672273d20ba2558b289e92d

dom/media/mediasource/TrackBuffersManager.cpp

@@ -211,6 +211,9 @@ TrackBuffersManager::ProcessTasks()
       mTaskQueue = nullptr;
       MOZ_DIAGNOSTIC_ASSERT(mQueue.Length() == 0,
                             "Detach task must be the last");
+      mVideoTracks.Reset();
+      mAudioTracks.Reset();
+      ShutdownDemuxers();
       return;
     default:
       NS_WARNING("Invalid Task");

dom/media/mediasource/TrackBuffersManager.h

@@ -376,10 +376,22 @@ private:
       mLastFrameDuration.reset();
       mHighestEndTimestamp.reset();
       mNeedRandomAccessPoint = true;
-
       mNextInsertionIndex.reset();
     }
 
+    void Reset()
+    {
+      ResetAppendState();
+      mEvictionIndex.Reset();
+      for (auto& buffer : mBuffers) {
+        buffer.Clear();
+      }
+      mSizeBuffer = 0;
+      mNextGetSampleIndex.reset();
+      mBufferedRanges.Clear();
+      mSanitizedBufferedRanges.Clear();
+    }
+
     void AddSizeOfResources(MediaSourceDecoder::ResourceSizes* aSizes) const;
   };