Add always on top windows to the alt+tab list

ash/wm/window_cycle_controller.h

 // Copyright (c) 2012 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 <list>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "ui/aura/client/activation_change_observer.h"
+#include "ui/aura/window_observer.h"
 
 namespace aura {
 class EventFilter;
+class RootWindow;
 class Window;
 }
 
 namespace ash {
 
 class WindowCycleList;
 
 // Controls cycling through windows with the keyboard, for example, 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.  Thus we maintain the state of the windows
+// 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 {
+class ASH_EXPORT WindowCycleController
+    : public aura::client::ActivationChangeObserver,
+      public aura::WindowObserver {
  public:
   enum Direction {
     FORWARD,
     BACKWARD
   };
   WindowCycleController();
-  ~WindowCycleController();
+  virtual ~WindowCycleController();
 
   // Returns true if cycling through windows is enabled. This is false at
   // certain times, such as when the lock screen is visible.
   static bool CanCycle();
 
   // Cycles between windows in the given |direction|. If |is_alt_down| then
   // interprets this call as the start of a multi-step cycle sequence and
   // installs a key filter to watch for alt being released.
   void HandleCycleWindow(Direction direction, bool is_alt_down);
 
   // Informs the controller that the Alt key has been released and it can
   // terminate the existing multi-step cycle.
   void AltKeyReleased();
 
   // Returns true if we are in the middle of a window cycling gesture.
   bool IsCycling() const { return windows_.get() != NULL; }
 
   // Returns the WindowCycleList. Really only useful for testing.
   const WindowCycleList* windows() const { return windows_.get(); }
 
+  // Set up the observers to handle window changes for the containers we care
+  // about.  Called when a new root window is added.
+  void OnRootWindowAdded(aura::RootWindow* root_window);
+
   // Returns the set of windows to cycle through. This method creates
   // the vector based on the current set of windows across all valid root
   // windows. As a result it is not necessarily the same as the set of
   // windows being iterated over.
-  static std::vector<aura::Window*> BuildWindowList();
+  // If |mru_windows| is not NULL, windows in this list are put at the head of
+  // the window list.
+  static std::vector<aura::Window*> BuildWindowList(
+      const std::list<aura::Window*>* mru_windows);
 
  private:
   // Call to start cycling windows.  You must call StopCycling() when done.
   void StartCycling();
 
   // Cycles to the next or previous window based on |direction|.
   void Step(Direction direction);
 
   // Installs an event filter to watch for release of the alt key.
   void InstallEventFilter();
 
   // Stops the current window cycle and cleans up the event filter.
   void StopCycling();
 
+  // Checks if the window represents a container whose children we track.
+  static bool IsTrackedContainer(aura::Window* window);
+
+  // Overridden from ActivationChangeObserver:
+  virtual void OnWindowActivated(aura::Window* active,
+                                 aura::Window* old_active) OVERRIDE;
+
+  // Overridden from WindowObserver:
+  virtual void OnWillRemoveWindow(aura::Window* window) OVERRIDE;
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
   scoped_ptr<WindowCycleList> windows_;
 
   // Event filter to watch for release of alt key.
   scoped_ptr<aura::EventFilter> event_filter_;
 
+  // List of windows that have been activated in containers that we cycle
+  // through, sorted by most recently used.
+  std::list<aura::Window*> mru_windows_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_