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

ui/events/gesture_detection/gesture_detector.h

 // 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.
 
 #ifndef UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_
 
 #include <memory>
 
 #include "base/logging.h"
@@ skipping 81 matching lines @@
   // Note: The listener must never be changed while |is_double_tapping| is true.
   void SetDoubleTapListener(DoubleTapListener* double_tap_listener);
 
   bool has_doubletap_listener() const { return double_tap_listener_ != NULL; }
 
   bool is_double_tapping() const { return is_double_tapping_; }
 
   void set_longpress_enabled(bool enabled) { longpress_enabled_ = enabled; }
   void set_showpress_enabled(bool enabled) { showpress_enabled_ = enabled; }
 
+  // Returns the event storing the initial position of the pointer with given
+  // pointer ID. The source could be either the current_down_event_ or
+  // secondary_pointer_down_event_.

[tdresser, 2016/07/22 19:51:28]

State that this returns nullptr if the source event isn't current or secondary.

[sahel, 2016/07/25 15:16:33]

Done.

+  const MotionEvent* GetSourcePointerDownEvent(
+      const MotionEvent& current_down_event,
+      const MotionEvent& secondary_pointer_down_event,
+      const int pointer_id);
+  int getPointerIndex(const MotionEvent& event, const int pointer_id);

[tdresser, 2016/07/22 19:51:28]

State that this returns -1 if it can't find it.

[sahel, 2016/07/25 15:16:33]

Done.

+
  private:
   void Init(const Config& config);
   void OnShowPressTimeout();
   void OnLongPressTimeout();
   void OnTapTimeout();
   void Cancel();
   void CancelTaps();
   bool IsRepeatedTap(const MotionEvent& first_down,
                      const MotionEvent& first_up,
                      const MotionEvent& second_down) const;
@@ skipping 58 matching lines @@
 
   // Determines speed during touch scrolling.
   VelocityTrackerState velocity_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureDetector);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_