Moves maintaining ShellObservers back to Shell

ash/high_contrast/high_contrast_controller.cc

 // Copyright (c) 2012 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/high_contrast/high_contrast_controller.h"
 
-#include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
 #include "ash/shell.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/compositor/layer.h"
 
 namespace ash {
 
 HighContrastController::HighContrastController() : enabled_(false) {
-  WmShell::Get()->AddShellObserver(this);
+  Shell::GetInstance()->AddShellObserver(this);
 }
 
 HighContrastController::~HighContrastController() {
-  WmShell::Get()->RemoveShellObserver(this);
+  Shell::GetInstance()->RemoveShellObserver(this);
 }
 
 void HighContrastController::SetEnabled(bool enabled) {
   enabled_ = enabled;
 
   // Update all active displays.
   aura::Window::Windows root_window_list = Shell::GetAllRootWindows();
   for (aura::Window::Windows::iterator it = root_window_list.begin();
        it != root_window_list.end(); it++) {
     UpdateDisplay(*it);
   }
 }
 
 void HighContrastController::UpdateDisplay(aura::Window* root_window) {
   root_window->layer()->SetLayerInverted(enabled_);
 }
 
 void HighContrastController::OnRootWindowAdded(WmWindow* root_window) {
   UpdateDisplay(WmWindow::GetAuraWindow(root_window));
 }
 
 }  // namespace ash