Slop region check for multi-finger scroll

ui/events/gesture_detection/gesture_detector.h

Index: ui/events/gesture_detection/gesture_detector.h
diff --git a/ui/events/gesture_detection/gesture_detector.h b/ui/events/gesture_detection/gesture_detector.h
index 4788be870eb6167a7d00b79c80ab9d81bb53d049..df5e6d5ec773a9b0b304ca139936c73cba7f99c6 100644
--- a/ui/events/gesture_detection/gesture_detector.h
+++ b/ui/events/gesture_detection/gesture_detector.h
@@ -110,6 +110,7 @@ class GESTURE_DETECTION_EXPORT GestureDetector {
                      const MotionEvent& first_up,
                      const MotionEvent& second_down) const;
   bool HandleSwipeIfNeeded(const MotionEvent& up, float vx, float vy);
+  bool IsWithinTouchSlop(const MotionEvent& ev);
 
   class TimeoutGestureHandler;
   std::unique_ptr<TimeoutGestureHandler> timeout_handler_;
@@ -130,7 +131,7 @@ class GESTURE_DETECTION_EXPORT GestureDetector {
 
   bool still_down_;
   bool defer_confirm_single_tap_;
-  bool always_in_tap_region_;
+  bool all_pointers_within_slop_regions_;
   bool always_in_bigger_tap_region_;
   bool two_finger_tap_allowed_for_gesture_;
 
@@ -148,6 +149,10 @@ class GESTURE_DETECTION_EXPORT GestureDetector {
   // disabled.
   bool is_down_candidate_for_repeated_single_tap_;
 
+  // Stores the maximum number of pointers that have been down simultaneously
+  // during the current touch sequence.
+  int maximum_pointer_count_;
+
   // The number of repeated taps in the current sequence, i.e., for the initial
   // tap this is 0, for the first *repeated* tap 1, etc...
   int current_single_tap_repeat_count_;