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

ui/views/widget/native_widget_win.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_win.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 
 #include <algorithm>
@@ skipping 738 matching lines @@
 
 void NativeWidgetWin::CloseNow() {
   // We may already have been destroyed if the selection resulted in a tab
   // switch which will have reactivated the browser window and closed us, so
   // we need to check to see if we're still a window before trying to destroy
   // ourself.
   if (IsWindow())
     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;
 
   ShowWindow(SW_SHOWNOACTIVATE);
   SetInitialFocus();
 }
 
 void NativeWidgetWin::Hide() {
   if (IsWindow()) {
@@ skipping 1721 matching lines @@
   return (GetKeyState(VK_LBUTTON) & 0x80) ||
     (GetKeyState(VK_RBUTTON) & 0x80) ||
     (GetKeyState(VK_MBUTTON) & 0x80) ||
     (GetKeyState(VK_XBUTTON1) & 0x80) ||
     (GetKeyState(VK_XBUTTON2) & 0x80);
 }
 
 }  // namespace internal
 
 }  // namespace views