Change RefPtr<DOMWrapperWorld> that causes reference cycles to DOMWrapperWorld*

Source/core/loader/FrameLoader.cpp

Index: Source/core/loader/FrameLoader.cpp
diff --git a/Source/core/loader/FrameLoader.cpp b/Source/core/loader/FrameLoader.cpp
index 6f83bfcd350c1c12172d2e96791eeb495ee3cc6e..5a93b286c41f553e8c2ee93b4a2ae24eddde6479 100644
--- a/Source/core/loader/FrameLoader.cpp
+++ b/Source/core/loader/FrameLoader.cpp
@@ -1442,10 +1442,10 @@ void FrameLoader::dispatchDidClearWindowObjectsInAllWorlds()
         page->inspectorController().didClearWindowObjectInMainWorld(m_frame);
     InspectorInstrumentation::didClearWindowObjectInMainWorld(m_frame);
 
-    Vector<RefPtr<DOMWrapperWorld> > worlds;
+    Vector<DOMWrapperWorld*> worlds;
     DOMWrapperWorld::allWorldsInMainThread(worlds);
     for (size_t i = 0; i < worlds.size(); ++i)
-        m_client->dispatchDidClearWindowObjectInWorld(worlds[i].get());
+        m_client->dispatchDidClearWindowObjectInWorld(worlds[i]);
 }
 
 void FrameLoader::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld* world)