Converts MruWindowTracker to work with common types

ash/wm/window_cycle_controller.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_WM_WINDOW_CYCLE_CONTROLLER_H_
 #define ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 
 namespace ui {
 class EventHandler;
 }
 
-namespace aura {
-class Window;
-}  // namespace aura
-
 namespace ash {
 
 class WindowCycleList;
+class WmWindow;
 
 // Controls cycling through windows with the keyboard via alt-tab.
 // Windows are sorted primarily by most recently used, and then by screen order.
 // We activate windows as you cycle through them, so the order on the screen
 // may change during the gesture, but the most recently used list isn't updated
 // until the cycling ends.  Thus we maintain the state of the windows
 // at the beginning of the gesture so you can cycle through in a consistent
 // order.
 class ASH_EXPORT WindowCycleController {
  public:
@@ skipping 28 matching lines @@
   }
 
  private:
   // Cycles to the next or previous window based on |direction|.
   void Step(Direction direction);
 
   std::unique_ptr<WindowCycleList> window_cycle_list_;
 
   // Tracks what Window was active when starting to cycle and used to determine
   // if the active Window changed in when ending cycling.
-  aura::Window* active_window_before_window_cycle_ = nullptr;
+  WmWindow* active_window_before_window_cycle_ = nullptr;
 
   // Event handler to watch for release of alt key.
   std::unique_ptr<ui::EventHandler> event_handler_;
 
   base::Time cycle_start_time_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_