Oilpan: add explicit Persistent<T>(T&) and Member<T>(T&) constructors.

Source/core/frame/DOMWindow.cpp

Index: Source/core/frame/DOMWindow.cpp
diff --git a/Source/core/frame/DOMWindow.cpp b/Source/core/frame/DOMWindow.cpp
index 05d1d218bd2fc9de8af4df4d5e498898b90b7531..7d2231f5fc46cb66a4b1801480ab2c4866d22f4f 100644
--- a/Source/core/frame/DOMWindow.cpp
+++ b/Source/core/frame/DOMWindow.cpp
@@ -113,7 +113,7 @@ class PostMessageTimer FINAL : public SuspendableTimer {
 public:
     PostMessageTimer(DOMWindow& window, PassRefPtr<SerializedScriptValue> message, const String& sourceOrigin, PassRefPtrWillBeRawPtr<DOMWindow> source, PassOwnPtr<MessagePortChannelArray> channels, SecurityOrigin* targetOrigin, PassRefPtr<ScriptCallStack> stackTrace, UserGestureToken* userGestureToken)
         : SuspendableTimer(window.document())
-        , m_window(&window)
+        , m_window(window)
         , m_message(message)
         , m_origin(sourceOrigin)
         , m_source(source)