Makes WorkspaceLayoutManager use ash/wm/common types

ash/switchable_windows.h

-// Copyright 2014 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_SWITCHABLE_WINDOWS_H_
-#define ASH_SWITCHABLE_WINDOWS_H_
-
-#include <stddef.h>
-
-#include "ash/ash_export.h"
-#include "base/macros.h"
-
-namespace aura {
-  class Window;
-}
-
-namespace ash {
-
-// List of containers which contain windows that can be switched via Alt+Tab to.
-ASH_EXPORT extern const int kSwitchableWindowContainerIds[];
-
-// The number of elements in kSwitchableWindowContainerIds.
-ASH_EXPORT extern const size_t kSwitchableWindowContainerIdsLength;
-
-// Returns true if |window| is a container for windows which can be switched to.
-ASH_EXPORT bool IsSwitchableContainer(const aura::Window* window);
-
-}  // namespace ash
-
-#endif  // ASH_SWITCHABLE_WINDOWS_H_