Oilpan: Allocate all EventTarget derived types on the manged heap.

Source/modules/webmidi/MIDIPort.h

Index: Source/modules/webmidi/MIDIPort.h
diff --git a/Source/modules/webmidi/MIDIPort.h b/Source/modules/webmidi/MIDIPort.h
index e8c5a59ff0c6de3671ab6519dcfc0b7e7288da48..96d3085e5ec857b19b64ef7fbf6d304cd663108e 100644
--- a/Source/modules/webmidi/MIDIPort.h
+++ b/Source/modules/webmidi/MIDIPort.h
@@ -43,7 +43,8 @@ namespace WebCore {
 class MIDIAccess;
 
 class MIDIPort : public RefCountedWillBeRefCountedGarbageCollected<MIDIPort>, public ScriptWrappable, public EventTargetWithInlineData {
-    DEFINE_EVENT_TARGET_REFCOUNTING(RefCountedWillBeRefCountedGarbageCollected<MIDIPort>);
+    REFCOUNTED_EVENT_TARGET(MIDIPort);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(MIDIPort);
 public:
     enum MIDIPortTypeCode {
         MIDIPortTypeInput,
@@ -60,7 +61,7 @@ public:
 
     MIDIAccess* midiAccess() const { return m_access; }
 
-    virtual void trace(Visitor*);
+    virtual void trace(Visitor*) OVERRIDE;
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(disconnect);