Revert EnableClose() removal and related crash fixes. I don't understand the crashes here, and th...

ui/views/widget/widget.h

Index: ui/views/widget/widget.h
===================================================================
--- ui/views/widget/widget.h	(revision 113407)
+++ ui/views/widget/widget.h	(working copy)
@@ -321,6 +321,10 @@
   // any code that expects it to be valid beyond this call.
   void CloseNow();
 
+  // Toggles the enable state for the Close button (and the Close menu item in
+  // the system menu).
+  void EnableClose(bool enable);
+
   // Shows or hides the widget, without changing activation state.
   virtual void Show();
   void Hide();