Remove leak of objects between isolated worlds on custom events.

Source/bindings/v8/custom/V8PopStateEventCustom.cpp

Index: Source/bindings/v8/custom/V8PopStateEventCustom.cpp
diff --git a/Source/bindings/v8/custom/V8PopStateEventCustom.cpp b/Source/bindings/v8/custom/V8PopStateEventCustom.cpp
index 43ac29ac220fb1fe3a44680d28495d7987644381..6843a2879dbb43f866187f7f35770066ec9ec51a 100644
--- a/Source/bindings/v8/custom/V8PopStateEventCustom.cpp
+++ b/Source/bindings/v8/custom/V8PopStateEventCustom.cpp
@@ -56,8 +56,9 @@ void V8PopStateEvent::stateAttrGetterCustom(v8::Local<v8::String> name, const v8
     }
 
     PopStateEvent* event = V8PopStateEvent::toNative(info.Holder());
-    if (!event->state().hasNoValue()) {
-        v8SetReturnValue(info, cacheState(info.Holder(), event->state().v8Value()));
+    v8::Handle<v8::Value> cachedState = info.Holder()->GetHiddenValue(V8HiddenPropertyName::state());
+    if (!cachedState.IsEmpty()) {
+        v8SetReturnValue(info, cachedState);
         return;
     }