Added UMA stats to overview mode

ash/wm/overview/window_grid.cc

 // Copyright 2014 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.
 
 #include "ash/wm/overview/window_grid.h"
 
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/overview/scoped_transform_overview_window.h"
@@ skipping 290 matching lines @@
   (*iter)->RemoveWindow(window);
 
   // If there are still windows in this selector entry then the overview is
   // still active and the active selection remains the same.
   if (!(*iter)->empty())
     return;
 
   size_t removed_index = iter - window_list_.begin();
   window_list_.erase(iter);
 
+  // Record that an item has been removed for statistical purposes.
+  window_selector_->on_window_removed();
+
   if (empty()) {
     // If the grid is now empty, notify the window selector so that it erases us
     // from its grid list.
     window_selector_->OnGridEmpty(this);
     return;
   }
 
   // If selecting, update the selection index.
   if (selection_widget_) {
     bool send_focus_alert = selected_index_ == removed_index;
@@ skipping 109 matching lines @@
         ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
     selection_widget_->SetBounds(SelectedWindow()->target_bounds());
     selection_widget_->SetOpacity(kWindowOverviewSelectorOpacity);
     return;
   }
   selection_widget_->SetBounds(SelectedWindow()->target_bounds());
   selection_widget_->SetOpacity(kWindowOverviewSelectorOpacity);
 }
 
 }  // namespace ash