Make ActiveScriptWrappable the GC mixin it is.

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

Index: third_party/WebKit/Source/modules/webaudio/ScriptProcessorNode.h
diff --git a/third_party/WebKit/Source/modules/webaudio/ScriptProcessorNode.h b/third_party/WebKit/Source/modules/webaudio/ScriptProcessorNode.h
index 8adb2d0ff3304bc9fbe0d967b555c53388ea5f14..a77b52e67394f076d8e5017ff9b2ea43dfc8022b 100644
--- a/third_party/WebKit/Source/modules/webaudio/ScriptProcessorNode.h
+++ b/third_party/WebKit/Source/modules/webaudio/ScriptProcessorNode.h
@@ -93,6 +93,7 @@ private:
 
 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.
@@ -110,6 +111,8 @@ public:
     // ActiveScriptWrappable
     bool hasPendingActivity() const final;
 
+    DEFINE_INLINE_VIRTUAL_TRACE() { AudioNode::trace(visitor); }
+
 private:
     ScriptProcessorNode(AbstractAudioContext&, float sampleRate, size_t bufferSize, unsigned numberOfInputChannels, unsigned numberOfOutputChannels);
 };