Make keyboard controller a singleton.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index b98378d26e4be872f1e152da2a378265036a5b37..29cd27c074185782e293f6626a9f3da9a25ec3cc 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -329,10 +329,6 @@ class ASH_EXPORT Shell
   // Test if the MaximizeModeWindowManager is enabled or not.
   bool IsMaximizeModeWindowManagerEnabled();
 
-  keyboard::KeyboardController* keyboard_controller() {
-    return keyboard_controller_.get();
-  }
-
   AcceleratorController* accelerator_controller() {
     return accelerator_controller_.get();
   }
@@ -621,7 +617,6 @@ class ASH_EXPORT Shell
   std::vector<WindowAndBoundsPair> to_restore_;
 
   scoped_ptr<UserMetricsRecorder> user_metrics_recorder_;
-  scoped_ptr<keyboard::KeyboardController> keyboard_controller_;
   scoped_ptr<NestedDispatcherController> nested_dispatcher_controller_;
   scoped_ptr<AcceleratorController> accelerator_controller_;
   scoped_ptr<ShellDelegate> delegate_;