Make keyboard controller a singleton.

ash/display/virtual_keyboard_window_controller.cc

 // Copyright 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.
 
 #include "ash/display/virtual_keyboard_window_controller.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/root_window_transformers.h"
@@ skipping 41 matching lines @@
 
     // No need to remove WindowTreeHostObserver because the DisplayController
     // outlives the host.
     host->AddObserver(Shell::GetInstance()->display_controller());
     InitRootWindowSettings(host->window())->display_id = display_info.id();
     host->InitHost();
     RootWindowController::CreateForVirtualKeyboardDisplay(host);
     root_window_controller_.reset(GetRootWindowController(host->window()));
     root_window_controller_->host()->Show();
     root_window_controller_->ActivateKeyboard(
-        Shell::GetInstance()->keyboard_controller());
+        keyboard::KeyboardController::GetInstance());
     FlipDisplay();
   } else {
     aura::WindowTreeHost* host = root_window_controller_->host();
     GetRootWindowSettings(host->window())->display_id = display_info.id();
     host->SetBounds(display_info.bounds_in_native());
   }
 }
 
 void VirtualKeyboardWindowController::Close() {
   if (root_window_controller_.get()) {
@@ skipping 26 matching lines @@
   Shell::GetInstance()->CreateKeyboard();
 }
 
 void VirtualKeyboardWindowController::OnMaximizeModeEnded() {
   keyboard::SetTouchKeyboardEnabled(false);
   if (!keyboard::IsKeyboardEnabled())
     Shell::GetInstance()->DeactivateKeyboard();
 }
 
 }  // namespace ash