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

ui/events/test/motion_event_test_utils.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/test/motion_event_test_utils.h"
 
 #include <sstream>
 
 #include "base/logging.h"
 #include "ui/events/base_event_utils.h"
@@ skipping 100 matching lines @@
   float dx = x - p.x;
   float dy = x - p.y;
   p.x = x;
   p.y = y;
   p.raw_x += dx;
   p.raw_y += dy;
   set_action(ACTION_MOVE);
   return *this;
 }
 
 MockMotionEvent& MockMotionEvent::ReleasePoint() {

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

It should be pretty easy to make this a thin wrapper of ReleasePointAt, right?
It would mean adding a bit of code to ReleasePointAt, but it would probably be
cleaner overall.

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

Done.

   UpdatePointersAndID();
   DCHECK_GT(GetPointerCount(), 0U);
   if (GetPointerCount() > 1) {
     set_action_index(static_cast<int>(GetPointerCount()) - 1);
     set_action(ACTION_POINTER_UP);
   } else {
     set_action(ACTION_UP);
   }
   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);
   set_action(ACTION_CANCEL);
   return *this;
 }
 
 MockMotionEvent& MockMotionEvent::SetTouchMajor(float new_touch_major) {
   for (size_t i = 0; i < GetPointerCount(); ++i)
     pointer(i).touch_major = new_touch_major;
@@ skipping 89 matching lines @@
         ss << ", ";
     }
     ss << "]\n}";
   }
 
   return ss.str();
 }
 
 }  // namespace test
 }  // namespace ui