Remove task.h and finish base::Bind() migration.

ash/shell.h

 // 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.
 
 #ifndef ASH_SHELL_H_
 #define ASH_SHELL_H_
 #pragma once
 
 #include <utility>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/task.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 
 class CommandLine;
 
 namespace aura {
 class EventFilter;
 class RootWindow;
 class Window;
 }
@@ skipping 135 matching lines @@
   // The |window_mode_| never changes after the shell is initialized.
   // Switching modes requires a restart.
   WindowMode window_mode_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_