Make ActiveScriptWrappable the GC mixin it is.

third_party/WebKit/Source/modules/webaudio/AudioScheduledSourceNode.h

 /*
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 104 matching lines @@
     double m_endTime; // in seconds
 
     static const double UnknownTime;
 private:
     // This is accessed by both the main thread and audio thread.  Use the setter and getter to
     // protect the access to this!
     int m_playbackState;
 };
 
 class AudioScheduledSourceNode : public AudioSourceNode, public ActiveScriptWrappable {
+    USING_GARBAGE_COLLECTED_MIXIN(AudioScheduledSourceNode);
 public:
     void start(ExceptionState&);
     void start(double when, ExceptionState&);
     void stop(ExceptionState&);
     void stop(double when, ExceptionState&);
 
     EventListener* onended();
     void setOnended(EventListener*);
 
     // ActiveScriptWrappable
     bool hasPendingActivity() const final;
 
+    DEFINE_INLINE_VIRTUAL_TRACE() { AudioSourceNode::trace(visitor); }
+
 protected:
     explicit AudioScheduledSourceNode(AbstractAudioContext&);
     AudioScheduledSourceHandler& audioScheduledSourceHandler() const;
 };
 
 } // namespace blink
 
 #endif // AudioScheduledSourceNode_h