Added UMA statistics for changing the active window via click or touch events.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index cb46540be67024994d76283a444bec82bd950b68..4f634b81aefe35de6c97b59ee8132fc5790a1bf9 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -69,6 +69,7 @@ class InputMethodEventFilter;
 class NestedAcceleratorController;
 class ShadowController;
 class VisibilityController;
+class WindowActivationPreTargetHandler;
 class WindowModalityController;
 }
 
@@ -119,6 +120,7 @@ class ResolutionNotificationController;
 class RootWindowController;
 class ScopedTargetRootWindow;
 class ScreenAsh;
+class ScreenEventTaskSwitchMetricRecorder;
 class ScreenOrientationController;
 class ScreenPositionController;
 class SessionStateDelegate;
@@ -678,6 +680,10 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   scoped_ptr<MagnificationController> magnification_controller_;
   scoped_ptr<PartialMagnificationController> partial_magnification_controller_;
   scoped_ptr<AutoclickController> autoclick_controller_;
+  scoped_ptr<::wm::WindowActivationPreTargetHandler>
+      window_activation_pretarget_handler_;
+  scoped_ptr<ScreenEventTaskSwitchMetricRecorder>
+      screen_event_task_switch_metric_recorder_;
   scoped_ptr<aura::client::FocusClient> focus_client_;
   aura::client::ActivationClient* activation_client_;
   scoped_ptr<PartialScreenshotController> partial_screenshot_controller_;