Add SourceBuffer implementations of Audio/VideoTracks

third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp

Index: third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp
diff --git a/third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp b/third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp
index 9e48afb2becb85d97f5f713249b3768643e65c95..f30f3062842a60579d6e19970d911c3bfca41cab 100644
--- a/third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp
+++ b/third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp
@@ -227,6 +227,18 @@ void SourceBuffer::setTimestampOffset(double offset, ExceptionState& exceptionSt
     m_timestampOffset = offset;
 }
 
+AudioTrackList& SourceBuffer::audioTracks()
+{
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+    return *m_audioTracks;
+}
+
+VideoTrackList& SourceBuffer::videoTracks()
+{
+    ASSERT(RuntimeEnabledFeatures::audioVideoTracksEnabled());
+    return *m_videoTracks;
+}
+
 double SourceBuffer::appendWindowStart() const
 {
     return m_appendWindowStart;
@@ -866,6 +878,8 @@ void SourceBuffer::didFail(FileError::ErrorCode errorCode)
 DEFINE_TRACE(SourceBuffer)
 {
     visitor->trace(m_source);
+    visitor->trace(m_audioTracks);
+    visitor->trace(m_videoTracks);
     visitor->trace(m_trackDefaults);
     visitor->trace(m_asyncEventQueue);
     visitor->trace(m_appendBufferAsyncPartRunner);