Make keyboard controller a singleton.

ui/keyboard/keyboard_controller.h

 // Copyright (c) 2013 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_KEYBOARD_KEYBOARD_CONTROLLER_H_
 #define UI_KEYBOARD_KEYBOARD_CONTROLLER_H_
 
 #include "base/basictypes.h"
 #include "base/event_types.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 63 matching lines @@
   virtual void AddObserver(KeyboardControllerObserver* observer);
   virtual void RemoveObserver(KeyboardControllerObserver* observer);
 
   KeyboardControllerProxy* proxy() { return proxy_.get(); }
 
   void set_lock_keyboard(bool lock) { lock_keyboard_ = lock; }
 
   // Force the keyboard to show up if not showing and lock the keyboard.
   void ShowAndLockKeyboard();
 
+  // Sets the active keyboard controller.

[sadrul, 2014/03/31 18:44:10]

Mention that the caller does not own the controller anymore (i.e.
KeyboardController takes ownership of the controller), and calling
ResetInstance() again will destroy the controller.

[kevers, 2014/04/01 15:57:10]

Done.

+  static void ResetInstance(KeyboardController* controller);
+
+  // Retrieve the active keyboard controller.
+  static KeyboardController* GetInstance();
+
  private:
   // For access to Observer methods for simulation.
   friend class KeyboardControllerTest;
 
   // aura::WindowObserver overrides
   virtual void OnWindowHierarchyChanged(
       const HierarchyChangeParams& params) OVERRIDE;
 
   // InputMethodObserver overrides
   virtual void OnTextInputTypeChanged(
@@ skipping 27 matching lines @@
 
   ui::InputMethod* input_method_;
   bool keyboard_visible_;
   bool lock_keyboard_;
   ui::TextInputType type_;
 
   ObserverList<KeyboardControllerObserver> observer_list_;
 
   base::WeakPtrFactory<KeyboardController> weak_factory_;
 
+  static KeyboardController* instance_;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardController);
 };
 
 }  // namespace keyboard
 
 #endif  // UI_KEYBOARD_KEYBOARD_CONTROLLER_H_