Eliminate pinch drift by removing touch radius from span calculation

ui/events/gesture_detection/scale_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_SCALE_GESTURE_DETECTOR_H_
 #define UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
@@ skipping 11 matching lines @@
  public:
   struct GESTURE_DETECTION_EXPORT Config {
     Config();
     ~Config();
 
     // Distance the current span can deviate from the initial span before
     // scaling will start (in dips). The span is the diameter of the circle with
     // a radius of average pointer deviation from the focal point.
     float span_slop;
 
-    // Minimum accepted value for TouchMajor while scaling (in dips).
-    float min_scaling_touch_major;
-
     // Minimum span needed to initiate a scaling gesture (in dips).
     float min_scaling_span;
 
     // Minimum pinch span change before pinch occurs (in dips). See
     // crbug.com/373318.
     float min_pinch_update_span_delta;
 
     // Whether the associated |ScaleGestureListener| should receive |OnScale|
     // callbacks when the user uses a stylus and presses the button.
     // Defaults to false.
@@ skipping 37 matching lines @@
   base::TimeDelta GetTimeDelta() const;
   base::TimeTicks GetEventTime() const;
 
  private:
   enum AnchoredScaleMode {
     ANCHORED_SCALE_MODE_NONE,
     ANCHORED_SCALE_MODE_DOUBLE_TAP,
     ANCHORED_SCALE_MODE_STYLUS
   };
 
-  // The TouchMajor/TouchMinor elements of a MotionEvent can flutter/jitter on
-  // some hardware/driver combos. Smooth out to get kinder, gentler behavior.
-  void AddTouchHistory(const MotionEvent& ev);
-  void ResetTouchHistory();
-
   void ResetScaleWithSpan(float span);
 
   ScaleGestureListener* const listener_;
   bool stylus_scale_enabled_;
 
   float focus_x_;
   float focus_y_;
   float curr_span_;
   float prev_span_;
   float initial_span_;
   float curr_span_x_;
   float curr_span_y_;
   float prev_span_x_;
   float prev_span_y_;
   base::TimeTicks curr_time_;
   base::TimeTicks prev_time_;
   bool in_progress_;
   float span_slop_;
   float min_span_;
 
-  // Bounds for recently seen values.
-  float touch_upper_;
-  float touch_lower_;
-  float touch_history_last_accepted_;
-  int touch_history_direction_;
-  base::TimeTicks touch_history_last_accepted_time_;
-  float touch_min_major_;
-  float touch_max_major_;
-
   float anchored_scale_start_x_;
   float anchored_scale_start_y_;
   AnchoredScaleMode anchored_scale_mode_;
 
   bool event_before_or_above_starting_gesture_event_;
 
   DISALLOW_COPY_AND_ASSIGN(ScaleGestureDetector);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_