ui::GestureProvider gives GestureEventData the number of touch points.

ui/events/gesture_detection/gesture_event_data.h

Index: ui/events/gesture_detection/gesture_event_data.h
diff --git a/ui/events/gesture_detection/gesture_event_data.h b/ui/events/gesture_detection/gesture_event_data.h
index f7f57a8b7defb37921059aaa58d3caae82c43ad3..4953284c76b1093002fbe3b804c788ddc91d1468 100644
--- a/ui/events/gesture_detection/gesture_event_data.h
+++ b/ui/events/gesture_detection/gesture_event_data.h
@@ -20,13 +20,15 @@ struct GESTURE_DETECTION_EXPORT GestureEventData {
                    base::TimeTicks time,
                    float x,
                    float y,
+                   int touch_point_count,
                    const GestureEventDetails& details);
 
   GestureEventData(EventType type,
                    int motion_event_id,
                    base::TimeTicks time,
                    float x,
-                   float y);
+                   float y,
+                   int touch_point_count);
 
   EventType type;
   int motion_event_id;