Makes KeyEvent struct traits restore Event::time_stamp() field

ui/events/event.h

Index: ui/events/event.h
diff --git a/ui/events/event.h b/ui/events/event.h
index 172746df713482408c9134fe3441cc3bd6cc52a7..d4a46afc802c8d7521c03faf842dd196aeb64979 100644
--- a/ui/events/event.h
+++ b/ui/events/event.h
@@ -817,7 +817,10 @@ class EVENTS_EXPORT KeyEvent : public Event {
 
   // Create a keystroke event from a legacy KeyboardCode.
   // This should not be used in new code.
-  KeyEvent(EventType type, KeyboardCode key_code, int flags);
+  KeyEvent(EventType type,
+           KeyboardCode key_code,
+           int flags,
+           base::TimeTicks time_stamp = base::TimeTicks());
 
   // Create a fully defined keystroke event.
   KeyEvent(EventType type,
@@ -828,7 +831,10 @@ class EVENTS_EXPORT KeyEvent : public Event {
            base::TimeTicks time_stamp);
 
   // Create a character event.
-  KeyEvent(base::char16 character, KeyboardCode key_code, int flags);
+  KeyEvent(base::char16 character,
+           KeyboardCode key_code,
+           int flags,
+           base::TimeTicks time_stamp = base::TimeTicks());
 
   // Used for synthetic events with code of DOM KeyboardEvent (e.g. 'KeyA')
   // See also: ui/events/keycodes/dom/dom_values.txt