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

ui/base/x/x11_util_internal.h

Index: ui/base/x/x11_util_internal.h
diff --git a/ui/base/x/x11_util_internal.h b/ui/base/x/x11_util_internal.h
index 70eb088c786e8668e48eb2f65f14f0d0a425a423..bfa381b78adcae58bbcb44c789ea35c44d560ea5 100644
--- a/ui/base/x/x11_util_internal.h
+++ b/ui/base/x/x11_util_internal.h
@@ -50,6 +50,19 @@ UI_EXPORT void SetX11ErrorHandlers(XErrorHandler error_handler,
 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_