Remove leak of objects between isolated worlds on custom events.

Source/core/dom/CustomEvent.h

Index: Source/core/dom/CustomEvent.h
diff --git a/Source/core/dom/CustomEvent.h b/Source/core/dom/CustomEvent.h
index 6afc0ae12a2e08192039934f61fca4e48a8d4e3a..3b8131c90334564d158ad7b19378bd3a96156bbc 100644
--- a/Source/core/dom/CustomEvent.h
+++ b/Source/core/dom/CustomEvent.h
@@ -35,7 +35,7 @@ namespace WebCore {
 struct CustomEventInit : public EventInit {
     CustomEventInit();
 
-    ScriptValue detail;
+    bool detailIsSet;
 };
 
 class CustomEvent : public Event {
@@ -52,20 +52,21 @@ public:
         return adoptRef(new CustomEvent(type, initializer));
     }
 
-    void initCustomEvent(const AtomicString& type, bool canBubble, bool cancelable, const ScriptValue& detail);
     void initCustomEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<SerializedScriptValue>);
 
     virtual const AtomicString& interfaceName() const;
 
-    const ScriptValue& detail() const { return m_detail; }
     PassRefPtr<SerializedScriptValue> serializedScriptValue() { return m_serializedScriptValue; }
 
+    bool isDetailSet() const { return m_detailIsSet; }
+
 private:
     CustomEvent();
     CustomEvent(const AtomicString& type, const CustomEventInit& initializer);
 
-    ScriptValue m_detail;
     RefPtr<SerializedScriptValue> m_serializedScriptValue;
+
+    bool m_detailIsSet;
 };
 
 } // namespace WebCore