Added UMA stats to overview mode

ash/wm/window_cycle_controller.h

Index: ash/wm/window_cycle_controller.h
diff --git a/ash/wm/window_cycle_controller.h b/ash/wm/window_cycle_controller.h
index d0da1f401251bfffc3fbe1accc308ddd4eac1667..4120bc05c48a5ec08b39efd5aa90d771187fe27d 100644
--- a/ash/wm/window_cycle_controller.h
+++ b/ash/wm/window_cycle_controller.h
@@ -8,6 +8,7 @@
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
 
 namespace ui {
 class EventHandler;
@@ -65,6 +66,8 @@ class ASH_EXPORT WindowCycleController {
   // Event handler to watch for release of alt key.
   scoped_ptr<ui::EventHandler> event_handler_;
 
+  base::Time cycle_start_time_;
+
   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
 };