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..f02e504253b6c8856bf384bca15c34714ffdc76e 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_always_in_tap_region_;

[tdresser, 2016/06/10 19:34:57]

Let's rename this to something like:
"all_pointers_within_slop_regions"

[sahel, 2016/06/23 22:34:44]

Done.

   bool always_in_bigger_tap_region_;
   bool two_finger_tap_allowed_for_gesture_;
 
@@ -148,6 +149,9 @@ class GESTURE_DETECTION_EXPORT GestureDetector {
   // disabled.
   bool is_down_candidate_for_repeated_single_tap_;
 
+  // Stores the maximum number of pointers that have been down together.

[tdresser, 2016/06/10 19:34:57]

The comment should make it clear that this is for the current touch sequence.

[sahel, 2016/06/23 22:34:44]

Done.

+  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_;