Add metrics to all items in the 'wrench' menu

chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h

Index: chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h
diff --git a/chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h b/chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h
index 4210a22e2deeeeeeb7bb62e7e81db6f874544626..1e0df0abb0d0a4a6d31fad4fe21f5f374ef95d22 100644
--- a/chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h
+++ b/chrome/browser/ui/toolbar/recent_tabs_sub_menu_model.h
@@ -9,6 +9,7 @@
 
 #include "base/memory/weak_ptr.h"
 #include "base/task/cancelable_task_tracker.h"
+#include "base/timer/elapsed_timer.h"
 #include "chrome/browser/favicon/favicon_service.h"
 #include "chrome/browser/sessions/tab_restore_service.h"
 #include "chrome/browser/sessions/tab_restore_service_observer.h"
@@ -171,6 +172,9 @@ class RecentTabsSubMenuModel : public ui::SimpleMenuModel,
 
   base::WeakPtrFactory<RecentTabsSubMenuModel> weak_ptr_factory_;
 
+  // Time the menu is open for until a recent tab is selected.
+  base::ElapsedTimer menu_opened_timer_;
+
   DISALLOW_COPY_AND_ASSIGN(RecentTabsSubMenuModel);
 };