Replace more ObserverList with base::ObserverList.

ui/base/ime/chromeos/ime_keyboard.h

 // Copyright 2014 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_IME_CHROMEOS_IME_KEYBOARD_H_
 #define UI_BASE_IME_CHROMEOS_IME_KEYBOARD_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 98 matching lines @@
       const std::string& layout_name);
 
   // Note: At this moment, classes other than InputMethodManager should not
   // instantiate the ImeKeyboard class.
   static UI_BASE_IME_EXPORT ImeKeyboard* Create();
 
   bool caps_lock_is_enabled_;
   std::string last_layout_;
 
  private:
-  ObserverList<Observer> observers_;
+  base::ObserverList<Observer> observers_;
 };
 
 }  // namespace input_method
 }  // namespace chromeos
 
 #endif  // UI_BASE_IME_CHROMEOS_IME_KEYBOARD_H_