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

ash/metrics/user_metrics_recorder.cc

Index: ash/metrics/user_metrics_recorder.cc
diff --git a/ash/metrics/user_metrics_recorder.cc b/ash/metrics/user_metrics_recorder.cc
index cfc4d8ee16d4a79a28fe463ce86ff38e8f60b497..8229039ea3e29e54e364fd0f4d36a715d7ee82de 100644
--- a/ash/metrics/user_metrics_recorder.cc
+++ b/ash/metrics/user_metrics_recorder.cc
@@ -4,6 +4,7 @@
 
 #include "ash/metrics/user_metrics_recorder.h"
 
+#include "ash/metrics/desktop_task_switch_metric_recorder.h"
 #include "ash/session/session_state_delegate.h"
 #include "ash/shelf/shelf_delegate.h"
 #include "ash/shelf/shelf_item_types.h"
@@ -236,6 +237,11 @@ void UserMetricsRecorder::RecordUserMetricsAction(UserMetricsAction action) {
     case ash::UMA_CLOSE_THROUGH_CONTEXT_MENU:
       base::RecordAction(base::UserMetricsAction("CloseFromContextMenu"));
       break;
+    case ash::UMA_DESKTOP_SWITCH_TASK:
+      base::RecordAction(base::UserMetricsAction("Desktop_SwitchTask"));
+      task_switch_metrics_recorder_.OnTaskSwitch(
+          TaskSwitchMetricsRecorder::kDesktop);
+      break;
     case ash::UMA_DRAG_MAXIMIZE_LEFT:
       base::RecordAction(base::UserMetricsAction("WindowDrag_MaximizeLeft"));
       break;
@@ -598,6 +604,19 @@ void UserMetricsRecorder::RecordUserMetricsAction(UserMetricsAction action) {
   }
 }
 
+void UserMetricsRecorder::OnShellInitialized() {
+  // Lazy creation of the DesktopTaskSwitchMetricRecorder because it accesses
+  // Shell::GetInstance() which is not available when |this| is instantiated.
+  if (!desktop_task_switch_metric_recorder_) {
+    desktop_task_switch_metric_recorder_.reset(
+        new DesktopTaskSwitchMetricRecorder());
+  }
+}
+
+void UserMetricsRecorder::OnShellShuttingDown() {
+  desktop_task_switch_metric_recorder_.reset();
+}
+
 void UserMetricsRecorder::RecordPeriodicMetrics() {
   ShelfLayoutManager* manager =
       ShelfLayoutManager::ForShelf(Shell::GetPrimaryRootWindow());