Added UMA stats to overview mode

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 98eb6524bcce5d78fcb7d15de34fdebf8b4b9ae6..11d274adde7ac2ded4e213f5b155846d3bf4bb7d 100644
--- a/ash/metrics/user_metrics_recorder.h
+++ b/ash/metrics/user_metrics_recorder.h
@@ -100,14 +100,15 @@ enum UserMetricsAction {
   UMA_WINDOW_MAXIMIZE_BUTTON_MAXIMIZE_LEFT,
   UMA_WINDOW_MAXIMIZE_BUTTON_MAXIMIZE_RIGHT,
 
-  // Thumbnail sized overview of windows triggered. This is a subset of
-  // UMA_WINDOW_SELECTION triggered by lingering during alt+tab cycles or
-  // pressing the overview key.
+  // Thumbnail sized overview of windows triggered by pressing the overview key.
   UMA_WINDOW_OVERVIEW,
 
-  // Window selection started by beginning an alt+tab cycle or pressing the
-  // overview key. This does not count each step through an alt+tab cycle.
-  UMA_WINDOW_SELECTION,
+  // Selecting a window in overview mode by pressing the enter key.
+  UMA_WINDOW_OVERVIEW_ENTER_KEY,
+
+  // Window selection started by beginning an alt+tab cycle. This does not count
+  // each step through an alt+tab cycle.
+  UMA_WINDOW_CYCLE,
 };
 
 // User Metrics Recorder provides a repeating callback (RecordPeriodicMetrics)