Have SourceBufferList trace all its object references.

Source/modules/mediasource/SourceBufferList.h

 /*
  * 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 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef SourceBufferList_h
 #define SourceBufferList_h
 
 #include "modules/EventTargetModules.h"
 #include "platform/heap/Handle.h"
-#include "wtf/Vector.h"
 
 namespace blink {
 
 class SourceBuffer;
 class GenericEventQueue;
 
 class SourceBufferList final : public RefCountedGarbageCollectedWillBeGarbageCollectedFinalized<SourceBufferList>, public EventTargetWithInlineData {
     DEFINE_EVENT_TARGET_REFCOUNTING_WILL_BE_REMOVED(RefCountedGarbageCollected<SourceBufferList>);
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(SourceBufferList);
@@ skipping 18 matching lines @@
     virtual const AtomicString& interfaceName() const override;
     virtual ExecutionContext* executionContext() const override;
 
     virtual void trace(Visitor*) override;
 
 private:
     SourceBufferList(ExecutionContext*, GenericEventQueue*);
 
     void scheduleEvent(const AtomicString&);
 
-    ExecutionContext* m_executionContext;
-    GenericEventQueue* m_asyncEventQueue;
+    RawPtrWillBeMember<ExecutionContext> m_executionContext;
+    RawPtrWillBeMember<GenericEventQueue> m_asyncEventQueue;
 
-    HeapVector<Member<SourceBuffer> > m_list;
+    HeapVector<Member<SourceBuffer>> m_list;
 };
 
 } // namespace blink
 
 #endif // SourceBufferList_h