Set the unique_event_id when converting from TouchEvent to WebTouchEvent

ui/events/gesture_detection/motion_event_generic.cc

Index: ui/events/gesture_detection/motion_event_generic.cc
diff --git a/ui/events/gesture_detection/motion_event_generic.cc b/ui/events/gesture_detection/motion_event_generic.cc
index 3789ec64657f5c516fd31800bddafd45dc667fac..13d2c0e0a83ac7296de991248db355e2589a8bce 100644
--- a/ui/events/gesture_detection/motion_event_generic.cc
+++ b/ui/events/gesture_detection/motion_event_generic.cc
@@ -73,6 +73,10 @@ int MotionEventGeneric::GetId() const {
   return id_;
 }
 
+uint64 MotionEventGeneric::GetUniqueId() const {
+  return unique_id_;
+}
+
 MotionEvent::Action MotionEventGeneric::GetAction() const {
   return action_;
 }