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

ash/wm/mru_window_tracker.h

Index: ash/wm/mru_window_tracker.h
diff --git a/ash/wm/mru_window_tracker.h b/ash/wm/mru_window_tracker.h
index abe7daa1fc71a47d6d342edacb506a34ba725240..f6cfabe59498559e770da9229c0a019d2878f38b 100644
--- a/ash/wm/mru_window_tracker.h
+++ b/ash/wm/mru_window_tracker.h
@@ -15,15 +15,13 @@
 
 namespace ash {
 
-class WmWindow;
-
 // Maintains a most recently used list of windows. This is used for window
 // cycling using Alt+Tab and overview mode.
 class ASH_EXPORT MruWindowTracker
     : public aura::client::ActivationChangeObserver,
       public aura::WindowObserver {
  public:
-  using WindowList = std::vector<WmWindow*>;
+  using WindowList = std::vector<aura::Window*>;
 
   MruWindowTracker();
   ~MruWindowTracker() override;
@@ -46,7 +44,7 @@ class ASH_EXPORT MruWindowTracker
  private:
   // Updates the mru_windows_ list to insert/move |active_window| at/to the
   // front.
-  void SetActiveWindow(WmWindow* active_window);
+  void SetActiveWindow(aura::Window* active_window);
 
   // Overridden from aura::client::ActivationChangeObserver:
   void OnWindowActivated(ActivationReason reason,
@@ -58,7 +56,7 @@ class ASH_EXPORT MruWindowTracker
 
   // List of windows that have been activated in containers that we cycle
   // through, sorted by most recently used.
-  std::list<WmWindow*> mru_windows_;
+  std::list<aura::Window*> mru_windows_;
 
   bool ignore_window_activations_;