[mus+ash] Removes WmWindow from ash/wm/mru_window_tracker and overview mode

ash/wm/focus_rules.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_FOCUS_RULES_H_
 #define ASH_WM_FOCUS_RULES_H_
 
 #include "ash/ash_export.h"
 
+namespace aura {
+class Window;
+}
+
 namespace ash {
 
-class WmWindow;
-
 // These functions provide the ash implementation wm::FocusRules. See
 // description there for details.
-ASH_EXPORT bool IsToplevelWindow(WmWindow* window);
-ASH_EXPORT bool IsWindowConsideredActivatable(WmWindow* window);
-ASH_EXPORT bool IsWindowConsideredVisibleForActivation(WmWindow* window);
+ASH_EXPORT bool IsToplevelWindow(aura::Window* window);
+ASH_EXPORT bool IsWindowConsideredActivatable(aura::Window* window);
+ASH_EXPORT bool IsWindowConsideredVisibleForActivation(aura::Window* window);
 
 }  // namespace ash
 
 #endif  // ASH_WM_FOCUS_RULES_H_