Added metrics to track the time between task switches done via Alt+Tab and Alt+Shift+Tab.

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 4120bc05c48a5ec08b39efd5aa90d771187fe27d..8cfd2a5820ee33541f7480806ea0b39d1ee124cf 100644
--- a/ash/wm/window_cycle_controller.h
+++ b/ash/wm/window_cycle_controller.h
@@ -14,6 +14,10 @@ namespace ui {
 class EventHandler;
 }
 
+namespace aura {
+class Window;
+}  // namespace aura
+
 namespace ash {
 
 class WindowCycleList;
@@ -63,6 +67,10 @@ class ASH_EXPORT WindowCycleController {
 
   scoped_ptr<WindowCycleList> window_cycle_list_;
 
+  // Tracks what Window was active when starting to cycle and used to determine
+  // if the active Window changed in when ending cycling.
+  aura::Window* active_window_before_window_cycle_ = nullptr;
+
   // Event handler to watch for release of alt key.
   scoped_ptr<ui::EventHandler> event_handler_;