Refactor access to scroll deltas in GesturePoint

ui/base/gestures/gesture_point.h

 // Copyright (c) 2012 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_BASE_GESTURES_GESTURE_POINT_H_
 #define UI_BASE_GESTURES_GESTURE_POINT_H_
 
 #include "base/basictypes.h"
 #include "ui/base/gestures/velocity_calculator.h"
 #include "ui/gfx/point.h"
@@ skipping 54 matching lines @@
   // A negative point_id indicates that the GesturePoint is not currently
   // associated with a touch.
   void set_point_id(int point_id) { point_id_ = point_id; }
   int point_id() const { return point_id_; }
 
   void set_touch_id(int touch_id) { touch_id_ = touch_id; }
   int touch_id() const { return touch_id_; }
 
   bool in_use() const { return point_id_ >= 0; }
 
-  double x_delta() const {
-    return last_touch_position_.x() - first_touch_position_.x();
-  }
-
-  double y_delta() const {
-    return last_touch_position_.y() - first_touch_position_.y();
-  }
+  gfx::Vector2d ScrollDelta();
 
   float XVelocity() { return velocity_calculator_.XVelocity(); }
   float YVelocity() { return velocity_calculator_.YVelocity(); }
 
   const gfx::Rect& enclosing_rectangle() const { return enclosing_rect_; }
 
  private:
   // Various statistical functions to manipulate gestures.
   bool IsInClickTimeWindow() const;
   bool IsInSecondClickTimeWindow() const;
   bool IsSecondClickInsideManhattanSquare(const TouchEvent& event) const;
   bool IsOverMinFlickSpeed();
 
   // The enclosing rectangle represents a rectangular touch region generated
   // by a sequence of ET_TOUCH_PRESSED, ET_TOUCH_MOVED, and ET_TOUCH_RELEASED
   // events forming a GESTURE_TAP event. The enclosing rectangle is updated
   // to be the union of the touch data from each of these events. It is
   // cleared on a ET_TOUCH_PRESSED event (i.e., at the beginning of a possible
   // GESTURE_TAP event) or when Reset is called.
   void UpdateEnclosingRectangle(const TouchEvent& event);
   void clear_enclosing_rectangle() { enclosing_rect_ = gfx::Rect(); }
 
-  // The position of touchdown event, or of the last scroll gesture event.
-  // We may want to consider tracking these two things in separate variables.
+  // The position of the first touchdown event.
   gfx::Point first_touch_position_;
   double first_touch_time_;
 
+  gfx::Point second_last_touch_position_;
+  double second_last_touch_time_;
+
   gfx::Point last_touch_position_;
   double last_touch_time_;
 
   double last_tap_time_;
   gfx::Point last_tap_position_;
 
   VelocityCalculator velocity_calculator_;
 
   int point_id_;
   int touch_id_;
 
   // Represents the rectangle that encloses the circles/ellipses
   // generated by a sequence of touch events
   gfx::Rect enclosing_rect_;
 
   DISALLOW_COPY_AND_ASSIGN(GesturePoint);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_GESTURES_GESTURE_POINT_H_