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

ash/metrics/task_switch_metrics_recorder.cc

Index: ash/metrics/task_switch_metrics_recorder.cc
diff --git a/ash/metrics/task_switch_metrics_recorder.cc b/ash/metrics/task_switch_metrics_recorder.cc
index b8b57fe4753606428c68f2be1236c100070d10c9..ec1e46475bf5f85431eb4952f30219fb4b10e702 100644
--- a/ash/metrics/task_switch_metrics_recorder.cc
+++ b/ash/metrics/task_switch_metrics_recorder.cc
@@ -5,11 +5,16 @@
 #include "ash/metrics/task_switch_metrics_recorder.h"
 
 #include "ash/metrics/task_switch_time_tracker.h"
+#include "ui/aura/window.h"
+#include "ui/wm/public/window_types.h"
 
 namespace ash {
 
 namespace {
 
+const char kDesktopHistogramName[] =
+    "Ash.Desktop.TimeBetweenNavigateToTaskSwitches";
+
 const char kShelfHistogramName[] =
     "Ash.Shelf.TimeBetweenNavigateToTaskSwitches";
 
@@ -32,6 +37,8 @@ const char* GetHistogramName(
       return kAppListHistogramName;
     case TaskSwitchMetricsRecorder::kOverviewMode:
       return kOverviewModeHistogramName;
+    case TaskSwitchMetricsRecorder::kDesktop:
+      return kDesktopHistogramName;
     case TaskSwitchMetricsRecorder::kShelf:
       return kShelfHistogramName;
     case TaskSwitchMetricsRecorder::kTabStrip:
@@ -64,6 +71,11 @@ void TaskSwitchMetricsRecorder::OnTaskSwitch(
   task_switch_time_tracker->OnTaskSwitch();
 }
 
+bool TaskSwitchMetricsRecorder::IsATaskWindow(aura::Window* window) const {
+  return window && (window->type() == ui::wm::WINDOW_TYPE_NORMAL ||
+                    window->type() == ui::wm::WINDOW_TYPE_PANEL);
+}
+
 TaskSwitchTimeTracker* TaskSwitchMetricsRecorder::FindTaskSwitchTimeTracker(
     TaskSwitchSource task_switch_source) {
   return histogram_map_.get(task_switch_source);