Oilpan: fix handling of SourceBuffer's async event queue.

Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 401 matching lines @@
 void SourceBuffer::removedFromMediaSource()
 {
     if (isRemoved())
         return;
 
     abortIfUpdating();
 
     m_webSourceBuffer->removedFromMediaSource();
     m_webSourceBuffer.clear();
     m_source = nullptr;
-    m_asyncEventQueue = 0;
+    m_asyncEventQueue = nullptr;
 }
 
 void SourceBuffer::initializationSegmentReceived()
 {
     ASSERT(m_source);
     ASSERT(m_updating);
 
     // https://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#sourcebuffer-init-segment-received
     // FIXME: Make steps 1-7 synchronous with this call.
     // FIXME: Augment the interface to this method to implement compliant steps 4-7 here.
@@ skipping 306 matching lines @@
 void SourceBuffer::didFail(FileError::ErrorCode errorCode)
 {
     WTF_LOG(Media, "SourceBuffer::didFail(%d) %p", errorCode, this);
     appendStreamDone(false);
 }
 
 void SourceBuffer::trace(Visitor* visitor)
 {
     visitor->trace(m_source);
     visitor->trace(m_stream);
+    visitor->trace(m_asyncEventQueue);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace blink