Change X11 error handler override to allow easy X11 error checking.

ui/base/x/x11_util_internal.h

 // 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.
 
 #ifndef UI_BASE_X_X11_UTIL_INTERNAL_H_
 #define UI_BASE_X_X11_UTIL_INTERNAL_H_
 #pragma once
 
 // This file declares utility functions for X11 (Linux only).
 //
@@ skipping 32 matching lines @@
 UI_EXPORT void SetX11ErrorHandlers(XErrorHandler error_handler,
                                    XIOErrorHandler io_error_handler);
 
 // NOTE: This function should not be called directly from the
 // X11 Error handler because it queries the server to decode the
 // error message, which may trigger other errors. A suitable workaround
 // is to post a task in the error handler to call this function.
 UI_EXPORT void LogErrorEventDescription(Display* dpy,
                                         const XErrorEvent& error_event);
 
+class ScopedX11ErrorHandlerOverride {
+ public:
+  ScopedX11ErrorHandlerOverride(XErrorHandler error_handler,
+                                XIOErrorHandler io_error_handler);
+  ~ScopedX11ErrorHandlerOverride();
+
+ private:
+  XErrorHandler old_error_handler_;
+  XIOErrorHandler old_io_error_handler_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(ScopedX11ErrorHandlerOverride);
+};
+
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_INTERNAL_H_