Remove leak of objects between isolated worlds on custom events.

Source/core/dom/PopStateEvent.cpp

Index: Source/core/dom/PopStateEvent.cpp
diff --git a/Source/core/dom/PopStateEvent.cpp b/Source/core/dom/PopStateEvent.cpp
index 072d28ba177377fa4f55318709e6094a4e0b8980..ea574de2ea9d8612687a17b0a4bdf10692aec3c2 100644
--- a/Source/core/dom/PopStateEvent.cpp
+++ b/Source/core/dom/PopStateEvent.cpp
@@ -47,9 +47,9 @@ PopStateEvent::PopStateEvent()
 
 PopStateEvent::PopStateEvent(const AtomicString& type, const PopStateEventInit& initializer)
     : Event(type, initializer)
-    , m_state(initializer.state)
     , m_serializedState(0)
     , m_history(0)
+    , m_stateIsSet(initializer.stateIsSet)
 {
     ScriptWrappable::init(this);
 }
@@ -58,6 +58,7 @@ PopStateEvent::PopStateEvent(PassRefPtr<SerializedScriptValue> serializedState,
     : Event(eventNames().popstateEvent, false, true)
     , m_serializedState(serializedState)
     , m_history(history)
+    , m_stateIsSet(false)
 {
     ScriptWrappable::init(this);
 }