[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..201802d5f649cf3de3fefa49714ab737ced7660a 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 +109,7 @@ void WindowCycleController::Step(Direction direction) {
 }
 
 void WindowCycleController::StopCycling() {
+  int depth = window_cycle_list_->current_index();

[tdanderson, 2016/06/24 19:25:56]

nit: no need for a local variable, just inline on line 123

[varkha, 2016/06/24 19:59:46]

|window_cycle_list_| goes away in the next line but I think I can move the UMA
statement here.

   window_cycle_list_.reset();
 
   WmWindow* active_window_after_window_cycle = GetActiveWindow(
@@ -116,6 +119,8 @@ void WindowCycleController::StopCycling() {
   event_handler_.reset();
   UMA_HISTOGRAM_MEDIUM_TIMES("Ash.WindowCycleController.CycleTime",
                              base::Time::Now() - cycle_start_time_);
+  UMA_HISTOGRAM_COUNTS_100("Ash.WindowCycleController.SelectionDepth",
+                           depth + 1);
 
   if (active_window_after_window_cycle != nullptr &&
       active_window_before_window_cycle_ != active_window_after_window_cycle) {