Get rid of the EnableClose() infrastructure in Widget.

ui/views/widget/native_widget_gtk.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/native_widget_gtk.h"
 
 #include <X11/Xatom.h>
 #include <X11/Xlib.h>
 #include <X11/extensions/shape.h>
 #include <gdk/gdk.h>
@@ skipping 1162 matching lines @@
                    close_widget_factory_.GetWeakPtr()));
   }
 }
 
 void NativeWidgetGtk::CloseNow() {
   if (widget_) {
     gtk_widget_destroy(widget_);  // Triggers OnDestroy().
   }
 }
 
-void NativeWidgetGtk::EnableClose(bool enable) {
-  gtk_window_set_deletable(GetNativeWindow(), enable);
-}
-
 void NativeWidgetGtk::Show() {
   if (widget_) {
     gtk_widget_show(widget_);
     if (widget_->window)
       gdk_window_raise(widget_->window);
   }
 }
 
 void NativeWidgetGtk::Hide() {
   if (widget_) {
@@ skipping 1106 matching lines @@
     button_pressed = event->type == GDK_BUTTON_PRESS ||
         event->type == GDK_2BUTTON_PRESS ||
         event->type == GDK_3BUTTON_PRESS;
     gdk_event_free(event);
   }
   return button_pressed;
 }
 
 }  // namespace internal
 }  // namespace views