Make ActiveScriptWrappable the GC mixin it is.

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

 /*
  * Copyright (C) 2010, 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 75 matching lines @@
 
     RefPtr<AudioBus> m_internalInputBus;
     // Synchronize process() with fireProcessEvent().
     mutable Mutex m_processEventLock;
 
     FRIEND_TEST_ALL_PREFIXES(ScriptProcessorNodeTest, BufferLifetime);
 };
 
 class ScriptProcessorNode final : public AudioNode, public ActiveScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
+    USING_GARBAGE_COLLECTED_MIXIN(ScriptProcessorNode);
 public:
     // bufferSize must be one of the following values: 256, 512, 1024, 2048,
     // 4096, 8192, 16384.
     // This value controls how frequently the onaudioprocess event handler is
     // called and how many sample-frames need to be processed each call.
     // Lower numbers for bufferSize will result in a lower (better)
     // latency. Higher numbers will be necessary to avoid audio breakup and
     // glitches.
     // The value chosen must carefully balance between latency and audio quality.
     static ScriptProcessorNode* create(AbstractAudioContext&, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels);
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(audioprocess);
     size_t bufferSize() const;
 
     // ActiveScriptWrappable
     bool hasPendingActivity() const final;
 
+    DEFINE_INLINE_VIRTUAL_TRACE() { AudioNode::trace(visitor); }
+
 private:
     ScriptProcessorNode(AbstractAudioContext&, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels);
 };
 
 } // namespace blink
 
 #endif // ScriptProcessorNode_h