Add UMA metrics for window selection and overview.

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>
 
 #include "ash/ash_export.h"
 #include "ash/wm/overview/window_selector.h"
 #include "ash/wm/overview/window_selector_delegate.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
 #include "ui/aura/window_observer.h"
 
 namespace aura {
 class Window;
 }
 
 namespace ash {
 
 namespace internal {
 class WindowSelectorTest;
@@ skipping 26 matching lines @@
   // Returns true if window selection mode is active.
   bool IsSelecting();
 
   // WindowSelectorDelegate:
   virtual void OnWindowSelected(aura::Window* window) OVERRIDE;
   virtual void OnSelectionCanceled() OVERRIDE;
 
  private:
   friend class internal::WindowSelectorTest;
 
+  // Dispatched when window selection begins.
+  void OnSelectionStarted();
+
   scoped_ptr<WindowSelector> window_selector_;
+  base::Time last_selection_time_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowSelectorController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_