Stop using "+chromeos(...)" in an XKB layout name.

chrome/browser/chromeos/input_method/mock_xkeyboard.cc

 // 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.
 
 #include "chrome/browser/chromeos/input_method/mock_xkeyboard.h"
 
 namespace chromeos {
 namespace input_method {
 
 MockXKeyboard::MockXKeyboard()
@@ skipping 35 matching lines @@
 }
 
 bool MockXKeyboard::NumLockIsEnabled() {
   return num_lock_is_enabled_;
 }
 
 bool MockXKeyboard::CapsLockIsEnabled() {
   return caps_lock_is_enabled_;
 }
 
-std::string MockXKeyboard::CreateFullXkbLayoutName(
-    const std::string& layout_name) {
-  return "";
-}
-
 unsigned int MockXKeyboard::GetNumLockMask() {
   return 1;
 }
 
 void MockXKeyboard::GetLockedModifiers(bool* out_caps_lock_enabled,
                                        bool* out_num_lock_enabled) {
   *out_caps_lock_enabled = caps_lock_is_enabled_;
   *out_num_lock_enabled = num_lock_is_enabled_;
 }
 
 }  // namespace input_method
 }  // namespace chromeos