Revert of Delete "shutdown without closing browsers" path

ash/shell.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/shell.h"
 
 #include <algorithm>
 #include <string>
 
 #include "ash/accelerators/accelerator_controller.h"
@@ skipping 612 matching lines @@
 #endif  // defined(OS_CHROMEOS)
 
 #if defined(OS_CHROMEOS)
   internal::PowerStatus::Initialize();
 #endif
 }
 
 Shell::~Shell() {
   TRACE_EVENT0("shutdown", "ash::Shell::Destructor");
 
-  delegate_->PreShutdown();
-
   views::FocusManagerFactory::Install(NULL);
 
   // Remove the focus from any window. This will prevent overhead and side
   // effects (e.g. crashes) from changing focus during shutdown.
   // See bug crbug.com/134502.
   aura::client::GetFocusClient(GetPrimaryRootWindow())->FocusWindow(NULL);
 
   // Please keep in same order as in Init() because it's easy to miss one.
   if (window_modality_controller_)
     window_modality_controller_.reset();
@@ skipping 470 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 // Shell, aura::client::ActivationChangeObserver implementation:
 
 void Shell::OnWindowActivated(aura::Window* gained_active,
                               aura::Window* lost_active) {
   if (gained_active)
     target_root_window_ = gained_active->GetRootWindow();
 }
 
 }  // namespace ash