Make Event RefCountedGarbageCollected and implement trace() methods to the Event hierarcy

Source/modules/webaudio/AudioProcessingEvent.cpp

Index: Source/modules/webaudio/AudioProcessingEvent.cpp
diff --git a/Source/modules/webaudio/AudioProcessingEvent.cpp b/Source/modules/webaudio/AudioProcessingEvent.cpp
index ac8eb99bcbc54bf9152e83b4af9af05f93dcc3dd..a00f779a81cf718736b197ce39d9cc0064698429 100644
--- a/Source/modules/webaudio/AudioProcessingEvent.cpp
+++ b/Source/modules/webaudio/AudioProcessingEvent.cpp
@@ -64,6 +64,11 @@ const AtomicString& AudioProcessingEvent::interfaceName() const
     return EventNames::AudioProcessingEvent;
 }
 
+void AudioProcessingEvent::trace(Visitor* visitor)
+{
+    Event::trace(visitor);
+}
+
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)