Missing source pointer down events are handled.

ui/events/gesture_detection/gesture_provider.cc

Index: ui/events/gesture_detection/gesture_provider.cc
diff --git a/ui/events/gesture_detection/gesture_provider.cc b/ui/events/gesture_detection/gesture_provider.cc
index 69956af36024c8ab37e10a3b9539e2dd22ebe0dc..1572b702d502d9e8419f383a0cea579c78c99c56 100644
--- a/ui/events/gesture_detection/gesture_provider.cc
+++ b/ui/events/gesture_detection/gesture_provider.cc
@@ -692,8 +692,8 @@ class GestureProvider::GestureListenerImpl : public ScaleGestureListener,
       const int pointer_id = ev2.GetPointerId(i);
       const MotionEvent* source_pointer_down_event =
           gesture_detector_.GetSourcePointerDownEvent(
-              ev1, secondary_pointer_down, pointer_id);
-      DCHECK(source_pointer_down_event);
+              ev1, &secondary_pointer_down, pointer_id);
+
       if (!source_pointer_down_event)
         continue;
       int source_index =