Fix browser_tests failure.

chrome/browser/chromeos/input_method/xkeyboard.h

 // Copyright (c) 2012 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 CHROME_BROWSER_CHROMEOS_INPUT_METHOD_XKEYBOARD_H_
 #define CHROME_BROWSER_CHROMEOS_INPUT_METHOD_XKEYBOARD_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 93 matching lines @@
 
   // Creates a full XKB layout name like
   //   "gb(extd)+chromeos(leftcontrol_disabled_leftalt),us"
   // from modifier key mapping and |layout_name|, such as "us", "us(dvorak)",
   // and "gb(extd)". Returns an empty string on error. Do not call this function
   // directly: it is public for testability.
   virtual std::string CreateFullXkbLayoutName(
       const std::string& layout_name,
       const ModifierMap& modifire_map) = 0;
 
-  // Returns a mask (e.g. 1U<<4) for Num Lock. On error, returns 0.
+  // Returns a mask (e.g. 1U<<4) for Num Lock. On error, returns 0. Do not call
+  // the function from non-UI threads.
   // TODO(yusukes): Move this and webdriver::GetXModifierMask() functions in
   // chrome/test/webdriver/keycode_text_conversion_x.cc to ui/base/x/x11_util.
   // The two functions are almost the same.
   virtual unsigned int GetNumLockMask() = 0;
 
   // Set true on |out_caps_lock_enabled| if Caps Lock is enabled. Set true on
   // |out_num_lock_enabled| if Num Lock is enabled. Both out parameters can be
   // NULL. Do not call the function from non-UI threads.
   virtual void GetLockedModifiers(bool* out_caps_lock_enabled,
                                   bool* out_num_lock_enabled) = 0;
@@ skipping 24 matching lines @@
 
   // Note: At this moment, classes other than InputMethodManager should not
   // instantiate the XKeyboard class.
   static XKeyboard* Create(const InputMethodUtil& util);
 };
 
 }  // namespace input_method
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_INPUT_METHOD_XKEYBOARD_H_