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

ui/views/widget/native_widget_win.cc

Index: ui/views/widget/native_widget_win.cc
===================================================================
--- ui/views/widget/native_widget_win.cc	(revision 113407)
+++ ui/views/widget/native_widget_win.cc	(working copy)
@@ -756,6 +756,13 @@
     DestroyWindow(hwnd());
 }
 
+void NativeWidgetWin::EnableClose(bool enable) {
+  // Disable the native frame's close button regardless of whether or not the
+  // native frame is in use, since this also affects the system menu.
+  EnableMenuItem(GetSystemMenu(GetNativeView(), false), SC_CLOSE, enable);
+  SendFrameChanged(GetNativeView());
+}
+
 void NativeWidgetWin::Show() {
   if (!IsWindow())
     return;