Makes WorkspaceLayoutManager use ash/wm/common types

ash/wm/common/fullscreen_window_finder.h

+// Copyright 2016 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_WM_COMMON_FULLSCREEN_WINDOW_FINDER_H_
+#define ASH_WM_COMMON_FULLSCREEN_WINDOW_FINDER_H_
+
+#include "ash/ash_export.h"
+
+namespace ash {
+namespace wm {
+
+class WmWindow;
+
+// Returns the topmost window or one of its transient parents, if any of them
+// are in fullscreen mode. This searches for a window in the root of |context|.
+ASH_EXPORT WmWindow* GetWindowForFullscreenMode(WmWindow* context);
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COMMON_FULLSCREEN_WINDOW_FINDER_H_