Added UMA stats to overview mode

ash/wm/overview/window_grid.cc

Index: ash/wm/overview/window_grid.cc
diff --git a/ash/wm/overview/window_grid.cc b/ash/wm/overview/window_grid.cc
index e59d078bf3accc0c87fd28249a6d8fe57e7d872c..66ce6de6fd457771c5c3f2360e9c7b9ec7692292 100644
--- a/ash/wm/overview/window_grid.cc
+++ b/ash/wm/overview/window_grid.cc
@@ -308,6 +308,8 @@ void WindowGrid::OnWindowDestroying(aura::Window* window) {
   size_t removed_index = iter - window_list_.begin();
   window_list_.erase(iter);
 
+  window_selector_->on_window_removed();

[tdanderson, 2014/06/09 17:50:45]

Perhaps include a comment that this call is only for the purpose of collecting
metrics.

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

Done.

+
   if (empty()) {
     // If the grid is now empty, notify the window selector so that it erases us
     // from its grid list.