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..9196a23f1a344fea77a1d2b8fb11cc2617e3ddc8 100644
--- a/ui/keyboard/keyboard_controller.h
+++ b/ui/keyboard/keyboard_controller.h
@@ -81,6 +81,14 @@ 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. KeyboardController takes ownership of
+  // the instance. Calling ResetIntance with a new instance destroys the
+  // previous one. May be called with NULL to clear the instance.
+  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 +136,8 @@ class KEYBOARD_EXPORT KeyboardController : public ui::InputMethodObserver,
 
   base::WeakPtrFactory<KeyboardController> weak_factory_;
 
+  static KeyboardController* instance_;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardController);
 };