[ash-md] Adds UMA items count and selection depth for Alt+Tab

ash/wm/window_cycle_controller.cc

Index: ash/wm/window_cycle_controller.cc
diff --git a/ash/wm/window_cycle_controller.cc b/ash/wm/window_cycle_controller.cc
index 5c37562341272bddc6778831ddfdc6f18b982d5b..752b7d7ff126593f99c69c92d8e31ebbcbd1db2b 100644
--- a/ash/wm/window_cycle_controller.cc
+++ b/ash/wm/window_cycle_controller.cc
@@ -96,6 +96,8 @@ void WindowCycleController::StartCycling() {
   event_handler_.reset(new WindowCycleEventFilter());
   cycle_start_time_ = base::Time::Now();
   WmShell::Get()->RecordUserMetricsAction(UMA_WINDOW_CYCLE);
+  UMA_HISTOGRAM_COUNTS_100("Ash.WindowCycleController.Items",
+                           window_list.size());
 }
 
 //////////////////////////////////////////////////////////////////////////////
@@ -107,6 +109,8 @@ void WindowCycleController::Step(Direction direction) {
 }
 
 void WindowCycleController::StopCycling() {
+  UMA_HISTOGRAM_COUNTS_100("Ash.WindowCycleController.SelectionDepth",
+                           window_cycle_list_->current_index() + 1);
   window_cycle_list_.reset();
 
   WmWindow* active_window_after_window_cycle = GetActiveWindow(