Simplify window.closed testing.

Source/core/frame/Frame.h

Index: Source/core/frame/Frame.h
diff --git a/Source/core/frame/Frame.h b/Source/core/frame/Frame.h
index fc4820a39d356845c767035bf6fba0adc6f83175..498cb77c81bfd740d26d1fdc0c02b6131f656796 100644
--- a/Source/core/frame/Frame.h
+++ b/Source/core/frame/Frame.h
@@ -98,9 +98,6 @@ public:
     // method.
     bool isRemoteFrameTemporary() const { return m_remotePlatformLayer; }
 
-    bool hasBeenClosed() const { return m_hasBeenClosed; }
-    void setHasBeenClosed();
-
 protected:
     Frame(FrameClient*, FrameHost*, FrameOwner*);
 
@@ -114,14 +111,6 @@ protected:
 private:
     FrameClient* m_client;
     blink::WebLayer* m_remotePlatformLayer;
-
-    // The closing of a frame by the embedder may not trigger the
-    // immediate release of this Frame object -- there might be
-    // other RefPtrs to the Frame, up the stack or elsewhere.
-    //
-    // Hence, keep a separate flag that's set when the frame is
-    // closed. It is consulted by window.closed.
-    bool m_hasBeenClosed;
 };
 
 inline FrameClient* Frame::client() const