Make keyboard controller a singleton.

ui/keyboard/keyboard_controller.h

Index: ui/keyboard/keyboard_controller.h
diff --git a/ui/keyboard/keyboard_controller.h b/ui/keyboard/keyboard_controller.h
index 86cd12dd760cccca9e7e359dc8a8105bf7b51012..a494e1e824fb587f923854629d2cc14b0176718b 100644
--- a/ui/keyboard/keyboard_controller.h
+++ b/ui/keyboard/keyboard_controller.h
@@ -81,6 +81,12 @@ class KEYBOARD_EXPORT KeyboardController : public ui::InputMethodObserver,
   // 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;
@@ -128,6 +134,8 @@ class KEYBOARD_EXPORT KeyboardController : public ui::InputMethodObserver,
 
   base::WeakPtrFactory<KeyboardController> weak_factory_;
 
+  static KeyboardController* instance_;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardController);
 };