Converts MruWindowTracker to work with common types

ash/wm/window_cycle_list.h

Index: ash/wm/window_cycle_list.h
diff --git a/ash/wm/window_cycle_list.h b/ash/wm/window_cycle_list.h
index a7d2156003bf0fd1df56a4e9d9424f3448072142..722f8ac52f63f9288f7fa02eba74b4df7e2b274c 100644
--- a/ash/wm/window_cycle_list.h
+++ b/ash/wm/window_cycle_list.h
@@ -9,10 +9,9 @@
 #include <vector>
 
 #include "ash/ash_export.h"
+#include "ash/common/wm_window_observer.h"
 #include "ash/wm/window_cycle_controller.h"
-#include "base/compiler_specific.h"
 #include "base/macros.h"
-#include "ui/aura/window_observer.h"
 
 namespace ash {
 
@@ -20,9 +19,9 @@ class ScopedShowWindow;
 
 // Tracks a set of Windows that can be stepped through. This class is used by
 // the WindowCycleController.
-class ASH_EXPORT WindowCycleList : public aura::WindowObserver {
+class ASH_EXPORT WindowCycleList : public WmWindowObserver {
  public:
-  typedef std::vector<aura::Window*> WindowList;
+  using WindowList = std::vector<WmWindow*>;
 
   explicit WindowCycleList(const WindowList& windows);
   ~WindowCycleList() override;
@@ -40,7 +39,7 @@ class ASH_EXPORT WindowCycleList : public aura::WindowObserver {
   // There is a chance a window is destroyed, for example by JS code. We need to
   // take care of that even if it is not intended for the user to close a window
   // while window cycling.
-  void OnWindowDestroying(aura::Window* window) override;
+  void OnWindowDestroying(WmWindow* window) override;
 
   // List of weak pointers to windows to use while cycling with the keyboard.
   // List is built when the user initiates the gesture (i.e. hits alt-tab the