Remove the singleton instance get/delete methods from RootWindow (yay)

chrome/browser/chrome_browser_main_extra_parts_aura.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 "chrome/browser/chrome_browser_main_extra_parts_aura.h"
 
 #include "ash/accelerators/accelerator_controller.h"
 #include "ash/ash_switches.h"
 #include "ash/shell.h"
 #include "base/command_line.h"
@@ skipping 59 matching lines @@
 void ChromeBrowserMainExtraPartsAura::PostProfileInit() {
   // Add the status area buttons after Profile has been initialized.
   if (!CommandLine::ForCurrentProcess()->HasSwitch(
         ash::switches::kAshUberTray)) {
     ChromeShellDelegate::instance()->status_area_host()->AddButtons();
   }
 }
 
 void ChromeBrowserMainExtraPartsAura::PostMainMessageLoopRun() {
   ash::Shell::DeleteInstance();
-  aura::RootWindow::DeleteInstance();
   aura::Env::DeleteInstance();
 }