The helper functions for slop region check and subtraction are modified.

ui/events/test/motion_event_test_utils.cc

Index: ui/events/test/motion_event_test_utils.cc
diff --git a/ui/events/test/motion_event_test_utils.cc b/ui/events/test/motion_event_test_utils.cc
index ec052913d1e26f60013330464186868e18415a4d..1bc5dbe229654697073d0eadce1733a3919b3a5b 100644
--- a/ui/events/test/motion_event_test_utils.cc
+++ b/ui/events/test/motion_event_test_utils.cc
@@ -130,6 +130,17 @@ MockMotionEvent& MockMotionEvent::ReleasePoint() {
   return *this;
 }
 
+MockMotionEvent& MockMotionEvent::ReleasePointAt(size_t index) {

[tdresser, 2016/07/22 15:57:45]

ReleasePointAtIndex?

It's a bit confusing that we have both ids and indices floating around, so it
would be nice to be explicit about which we're referring to.

[sahel, 2016/07/22 19:46:42]

Done.

+  DCHECK_LT(index, GetPointerCount());
+  if (index == GetPointerCount() - 1)
+    return ReleasePoint();
+  set_unique_event_id(ui::GetNextTouchEventId());
+  RemovePointerAt(index);
+  set_action_index(index);
+  set_action(ACTION_POINTER_UP);
+  return *this;
+}
+
 MockMotionEvent& MockMotionEvent::CancelPoint() {
   UpdatePointersAndID();
   DCHECK_GT(GetPointerCount(), 0U);