Add metrics for DelayNavigationThrottle

chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h

Index: chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h
diff --git a/chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h b/chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h
index cea38df156b147e320fd30f7ce4fddf6f96ad800..6456f3a247fe9a3ef4bab21317478a2ca5732db3 100644
--- a/chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h
+++ b/chrome/browser/page_load_metrics/experiments/delay_navigation_throttle.h
@@ -60,6 +60,9 @@ class DelayNavigationThrottle : public content::NavigationThrottle {
   const scoped_refptr<base::TaskRunner> task_runner_;
   const base::TimeDelta navigation_delay_;
 
+  // The time we added a delay to this navigation.
+  base::TimeTicks delay_start_time_;
+
   // This has to be the last member of the class.
   base::WeakPtrFactory<DelayNavigationThrottle> weak_ptr_factory_;