New scroll latency metrics added for touch and wheel.

ui/events/latency_info.h

Index: ui/events/latency_info.h
diff --git a/ui/events/latency_info.h b/ui/events/latency_info.h
index 606cfd40a39ea9273d983649b092b20c788761ac..abb52dc1d600e8f3e3d50772db99a237bce66293 100644
--- a/ui/events/latency_info.h
+++ b/ui/events/latency_info.h
@@ -137,6 +137,10 @@ class EVENTS_BASE_EXPORT LatencyInfo {
     base::TimeTicks event_time;
     // Count of events that happened in this component
     uint32_t event_count;
+    // Time of the oldest event that happened in this component.
+    base::TimeTicks first_event_time;
+    // Time of the most recent event that happened in this component.
+    base::TimeTicks last_event_time;
   };
 
   // Empirically determined constant based on a typical scroll sequence.