Fix undefined reference errors in input_method_engine.cc for Chrome OS build.

chrome/browser/chromeos/input_method/ibus_keymap.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 "chrome/browser/chromeos/input_method/ibus_keymap.h"
 
 #if defined(HAVE_IBUS)
 #include <ibus.h>
 #endif
 
+namespace chromeos {
+namespace input_method {
+
 #if defined(HAVE_IBUS)
 std::string GetIBusKey(int keyval) {
   // TODO: Ensure all keys are supported.
   switch (keyval) {
     case IBUS_Escape:
       return "Esc";
     case IBUS_F1:
       return "HistoryBack";
     case IBUS_F2:
       return "HistoryForward";
@@ skipping 58 matching lines @@
 }
 #else
 std::string GetIBusKey(int keyval, int keycode) {
   return "";
 }
 
 std::string GetIBusKeyCode(int keyval, int keycode) {
   return "";
 }
 #endif // HAVE_IBUS
+
+}  // namespace input_method
+}  // namespace chromeos