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 667c7e4ffc7fe2eb1fdf47a9504fff50801de531..08c96bcea62924a78071e7e8d6b7a155576ea31d 100644
--- a/ash/metrics/task_switch_metrics_recorder.cc
+++ b/ash/metrics/task_switch_metrics_recorder.cc
@@ -13,12 +13,17 @@ namespace {
 const char kShelfHistogramName[] =
     "Ash.Shelf.TimeBetweenNavigateToTaskSwitches";
 
+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::kShelf:
       return kShelfHistogramName;
+    case TaskSwitchMetricsRecorder::kOverviewMode:
+      return kOverviewModeHistogramName;
   }
   NOTREACHED();
   return nullptr;