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

Source/core/events/EventTarget.h

Index: Source/core/events/EventTarget.h
diff --git a/Source/core/events/EventTarget.h b/Source/core/events/EventTarget.h
index 8f7c238282c6b60496e82fb07be2ec55c186ba23..44b4ead1add6e245554d4bb8fe5c63e8fa45e722 100644
--- a/Source/core/events/EventTarget.h
+++ b/Source/core/events/EventTarget.h
@@ -72,7 +72,7 @@ public:
     OwnPtr<FiringEventIteratorVector> firingEventIterators;
 };
 
-class EventTarget {
+class EventTarget : public WillBeGarbageCollectedMixin {
 public:
     void ref() { refEventTarget(); }
     void deref() { derefEventTarget(); }
@@ -110,6 +110,8 @@ public:
 
     bool fireEventListeners(Event*);
 
+    virtual void trace(Visitor*) { }
+
 protected:
     virtual ~EventTarget();
 
@@ -223,6 +225,6 @@ private: \
 // Use this macro if your EventTarget subclass is also a subclass of WTF::RefCounted.
 // A ref-counted class that uses a different method of refcounting should use DEFINE_EVENT_TARGET_REFCOUNTING directly.
 // Both of these macros are meant to be placed just before the "public:" section of the class declaration.
-#define REFCOUNTED_EVENT_TARGET(className) DEFINE_EVENT_TARGET_REFCOUNTING(RefCounted<className>)
+#define REFCOUNTED_EVENT_TARGET(className) DEFINE_EVENT_TARGET_REFCOUNTING(RefCountedWillBeRefCountedGarbageCollected<className>)
 
 #endif // EventTarget_h