Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

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 <utility>
 
@@ skipping 77 matching lines @@
 #include "ash/wm/toplevel_window_event_handler.h"
 #include "ash/wm/video_detector.h"
 #include "ash/wm/window_animations.h"
 #include "ash/wm/window_properties.h"
 #include "ash/wm/window_util.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "base/sys_info.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/trace_event/trace_event.h"
 #include "chromeos/audio/audio_a11y_controller.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/system/devicemode.h"
 #include "services/service_manager/public/cpp/connector.h"
 #include "services/ui/public/interfaces/constants.mojom.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/env.h"
 #include "ui/aura/layout_manager.h"
@@ skipping 829 matching lines @@
 std::unique_ptr<ui::EventTargetIterator> Shell::GetChildIterator() const {
   return std::unique_ptr<ui::EventTargetIterator>();
 }
 
 ui::EventTargeter* Shell::GetEventTargeter() {
   NOTREACHED();
   return nullptr;
 }
 
 }  // namespace ash