Record time between switching the active window from Ash overview mode

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 a22602cda3c5bf17fd4c14c7799d1c8f2df4df59..82b9e38329d55d152eecfab0f6a888710d7412fa 100644
--- a/ash/metrics/task_switch_metrics_recorder.cc
+++ b/ash/metrics/task_switch_metrics_recorder.cc
@@ -16,10 +16,15 @@ const char kShelfHistogramName[] =
 const char kAcceleratorWindowCycleHistogramName[] =
     "Ash.WindowCycleController.TimeBetweenTaskSwitches";
 
+const char kOverviewModeHistogramName[] =
+    "Ash.WindowSelector.TimeBetweenActiveWindowChanges";
+
 // Returns the histogram name for the given |task_switch_source|.
 const char* GetHistogramName(
     TaskSwitchMetricsRecorder::TaskSwitchSource task_switch_source) {
   switch (task_switch_source) {
+    case TaskSwitchMetricsRecorder::kOverviewMode:
+      return kOverviewModeHistogramName;
     case TaskSwitchMetricsRecorder::kShelf:
       return kShelfHistogramName;
     case TaskSwitchMetricsRecorder::kWindowCycleController: