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

ash/metrics/user_metrics_recorder.h

Index: ash/metrics/user_metrics_recorder.h
diff --git a/ash/metrics/user_metrics_recorder.h b/ash/metrics/user_metrics_recorder.h
index 7bb6f9d52d992bd59518523a4cd44733c4f2bb23..0d22355f62317069da19f55080ee57567cccbd8c 100644
--- a/ash/metrics/user_metrics_recorder.h
+++ b/ash/metrics/user_metrics_recorder.h
@@ -7,10 +7,13 @@
 
 #include "ash/ash_export.h"
 #include "ash/metrics/task_switch_metrics_recorder.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/timer/timer.h"
 
 namespace ash {
 
+class DesktopTaskSwitchMetricRecorder;
+
 namespace test {
 class UserMetricsRecorderTestAPI;
 }
@@ -27,6 +30,7 @@ enum UserMetricsAction {
   UMA_ACCEL_RESTART_POWER_BUTTON,
   UMA_ACCEL_SHUT_DOWN_POWER_BUTTON,
   UMA_CLOSE_THROUGH_CONTEXT_MENU,
+  UMA_DESKTOP_SWITCH_TASK,
   UMA_DRAG_MAXIMIZE_LEFT,
   UMA_DRAG_MAXIMIZE_RIGHT,
   UMA_GESTURE_OVERVIEW,
@@ -153,6 +157,12 @@ class ASH_EXPORT UserMetricsRecorder {
     return task_switch_metrics_recorder_;
   }
 
+  // Informs |this| that the Shell has been initialized.
+  void OnShellInitialized();
+
+  // Informs |this| that the Shell is going to be shut down.
+  void OnShellShuttingDown();
+
  private:
   friend class test::UserMetricsRecorderTestAPI;
 
@@ -179,6 +189,11 @@ class ASH_EXPORT UserMetricsRecorder {
 
   TaskSwitchMetricsRecorder task_switch_metrics_recorder_;
 
+  // Metric recorder to track how often task windows are activated by mouse
+  // clicks or touchscreen taps.
+  scoped_ptr<DesktopTaskSwitchMetricRecorder>
+      desktop_task_switch_metric_recorder_;
+
   DISALLOW_COPY_AND_ASSIGN(UserMetricsRecorder);
 };