Remove keyboard usability mode

ash/display/display_controller.h

Index: ash/display/display_controller.h
diff --git a/ash/display/display_controller.h b/ash/display/display_controller.h
index 988f1389701776a9611732c33cfb6457c15388b8..e1d33017bbf045cc6b404c991f5008e6b566832f 100644
--- a/ash/display/display_controller.h
+++ b/ash/display/display_controller.h
@@ -90,10 +90,6 @@ class ASH_EXPORT DisplayController : public gfx::DisplayObserver,
     return mirror_window_controller_.get();
   }
 
-  VirtualKeyboardWindowController* virtual_keyboard_window_controller() {
-    return virtual_keyboard_window_controller_.get();
-  }
-
   // Create a WindowTreeHost for the primary display. This replaces
   // |initial_bounds| in |init_params|.
   void CreatePrimaryHost(const AshWindowTreeHostInitParams& init_params);
@@ -216,8 +212,6 @@ class ASH_EXPORT DisplayController : public gfx::DisplayObserver,
 
   scoped_ptr<CursorWindowController> cursor_window_controller_;
   scoped_ptr<MirrorWindowController> mirror_window_controller_;
-  scoped_ptr<VirtualKeyboardWindowController>
-      virtual_keyboard_window_controller_;
 
   // Stores the curent cursor location (in native coordinates) used to
   // restore the cursor location when display configuration