Track input latency with UMA stats

ui/base/events/event_utils.h

Index: ui/base/events/event_utils.h
diff --git a/ui/base/events/event_utils.h b/ui/base/events/event_utils.h
index 77e542f04922732094b4f532fb82b7cf6bd0f7c6..49a6b090b208ff45aa9776403ba58b8d855d9cfe 100644
--- a/ui/base/events/event_utils.h
+++ b/ui/base/events/event_utils.h
@@ -35,9 +35,13 @@ UI_EXPORT EventType EventTypeFromNative(const base::NativeEvent& native_event);
 // Get the EventFlags from a native event.
 UI_EXPORT int EventFlagsFromNative(const base::NativeEvent& native_event);
 
+// Get the timestamp from a native event.
 UI_EXPORT base::TimeDelta EventTimeFromNative(
     const base::NativeEvent& native_event);
 
+// Create a timestamp based on the current time.
+UI_EXPORT base::TimeDelta EventTimeForNow();
+
 // Get the location from a native event.  The coordinate system of the resultant
 // |Point| has the origin at top-left of the "root window".  The nature of
 // this "root window" and how it maps to platform-specific drawing surfaces is