Added UMA stats to overview mode

ash/wm/overview/window_selector.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_H_
 #define ASH_WM_OVERVIEW_WINDOW_SELECTOR_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 48 matching lines @@
   WindowSelector(const WindowList& windows,
                  WindowSelectorDelegate* delegate);
   virtual ~WindowSelector();
 
   // Cancels window selection.
   void CancelSelection();
 
   // Called when the last window selector item from a grid is deleted.
   void OnGridEmpty(WindowGrid* grid);
 
+  // Called when removing a window, adds one to the closed window counter.
+  void on_window_removed() { num_closed_items_++; }
+
   // ui::EventHandler:
   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
 
   // gfx::DisplayObserver:
   virtual void OnDisplayAdded(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayRemoved(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayMetricsChanged(const gfx::Display& display,
                                        uint32_t metrics) OVERRIDE;
 
   // aura::WindowObserver:
@@ skipping 38 matching lines @@
   // this window.
   aura::Window* restore_focus_window_;
 
   // True when performing operations that may cause window activations. This is
   // used to prevent handling the resulting expected activation.
   bool ignore_activations_;
 
   // List of all the window overview grids, one for each root window.
   ScopedVector<WindowGrid> grid_list_;
 
-  // The time when overview was started.
-  base::Time overview_start_time_;
-
   // Tracks windows which were hidden because they were not part of the
   // overview.
   aura::WindowTracker hidden_windows_;
 
   // Tracks the index of the root window the selection widget is in.
   size_t selected_grid_index_;
 
+  // The time when overview was started.
+  base::Time overview_start_time_;

[tdanderson, 2014/06/09 17:50:46]

Similar to my other comment, it might be good to include a comment for the new
member variables you're adding to say that they're only being used for metrics.

[Nina, 2014/06/09 18:12:50]

Done.

+
+  // The number of arrow key presses for this particular overview session.
+  size_t num_key_presses_;
+
+  // The number of items in the overview.
+  size_t num_items_;
+
+  // The number of items that were removed from the overview.

[tdanderson, 2014/06/09 17:50:46]

Similar to |num_key_presses_|, clarify that this counter is for a single
overview session only and is not cumulative.

[Nina, 2014/06/09 18:12:50]

I clarified this with a general comment.

+  size_t num_closed_items_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowSelector);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERVIEW_WINDOW_SELECTOR_H_