Get rid of the EnableClose() infrastructure in Widget.

ui/views/window/non_client_view.h

Index: ui/views/window/non_client_view.h
===================================================================
--- ui/views/window/non_client_view.h	(revision 111086)
+++ ui/views/window/non_client_view.h	(working copy)
@@ -53,7 +53,6 @@
   virtual int NonClientHitTest(const gfx::Point& point) = 0;
   virtual void GetWindowMask(const gfx::Size& size,
                              gfx::Path* window_mask) = 0;
-  virtual void EnableClose(bool enable) = 0;
   virtual void ResetWindowControls() = 0;
   virtual void UpdateWindowIcon() = 0;
 
@@ -175,10 +174,6 @@
   // size. This is used to create the non-rectangular window shape.
   void GetWindowMask(const gfx::Size& size, gfx::Path* window_mask);
 
-  // Toggles the enable state for the Close button (and the Close menu item in
-  // the system menu).
-  void EnableClose(bool enable);
-
   // Tells the window controls as rendered by the NonClientView to reset
   // themselves to a normal state. This happens in situations where the
   // containing window does not receive a normal sequences of messages that