Oilpan: Prepare to move EventHandler to Oilpan heap.

Source/core/frame/LocalFrame.h

Index: Source/core/frame/LocalFrame.h
diff --git a/Source/core/frame/LocalFrame.h b/Source/core/frame/LocalFrame.h
index 1148f38812dd90a487e4ca89e52de943f0856afb..0dbcceb93845fe92fdff4d8b6b4996119dfef184 100644
--- a/Source/core/frame/LocalFrame.h
+++ b/Source/core/frame/LocalFrame.h
@@ -164,7 +164,7 @@ namespace WebCore {
         const OwnPtrWillBePersistent<Editor> m_editor;
         const OwnPtr<SpellChecker> m_spellChecker;
         const OwnPtrWillBePersistent<FrameSelection> m_selection;
-        const OwnPtr<EventHandler> m_eventHandler;
+        const OwnPtrWillBePersistent<EventHandler> m_eventHandler;
         const OwnPtr<FrameConsole> m_console;
         OwnPtr<InputMethodController> m_inputMethodController;