Add user action for changing the active window in Ash overview mode

ash/wm/overview/window_selector_controller.h

 // Copyright 2013 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_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 #define ASH_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 
 #include <list>
 #include <vector>
 
@@ skipping 36 matching lines @@
   // Returns true if overview mode is restoring minimized windows so that they
   // are visible during overview mode.
   bool IsRestoringMinimizedWindows() const;
 
   // WindowSelectorDelegate:
   void OnSelectionEnded() override;
 
  private:
   friend class WindowSelectorTest;
 
-  // Dispatched when window selection begins.
+  // Called when overview mode is about to be engaged.
+  void OnSelectionStarting();
+
+  // Called when overview mode is engaged.
   void OnSelectionStarted();
 
   scoped_ptr<WindowSelector> window_selector_;
   base::Time last_selection_time_;
 
+  // While overview mode is active, tracks the window of type WINDOW_TYPE_NORMAL
+  // or WINDOW_TYPE_PANEL that was active prior to entering overview mode if
+  // such a window exists (nullptr otherwise).

[oshima, 2015/05/12 20:25:13]

document that the pointer may be stale (if it's closed during overview mode).
you may actually reset the pointer when the window is destroyed, but I'll leave
it to you, as its content isn't accessed.

[tdanderson, 2015/05/14 01:36:32]

I've removed this pointer in patch set 2.

+  aura::Window* initially_active_window_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowSelectorController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_