gesture recognizer: Fix computing the bounding box of the rectangles.

ui/base/gestures/gesture_sequence.cc

 // 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.
 
 #include "ui/base/gestures/gesture_sequence.h"
 
 #include <cmath>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 653 matching lines @@
         location,
         flags_,
         base::Time::FromDoubleT(point.last_touch_time()),
         1 << point.touch_id()));
   }
 }
 
 void GestureSequence::AppendScrollGestureUpdate(const GesturePoint& point,
                                                 const gfx::Point& location,
                                                 Gestures* gestures) {
-  int dx = location.x() - bounding_box_last_center_.x();
-  int dy = location.y() - bounding_box_last_center_.y();
+  gfx::Point current_center = bounding_box_.CenterPoint();
+  int dx = current_center.x() - bounding_box_last_center_.x();
+  int dy = current_center.y() - bounding_box_last_center_.y();
   if (dx == 0 && dy == 0)
     return;
   if (scroll_type_ == ST_HORIZONTAL)
     dy = 0;
   else if (scroll_type_ == ST_VERTICAL)
     dx = 0;
 
   gestures->push_back(CreateGestureEvent(
       GestureEventDetails(ui::ET_GESTURE_SCROLL_UPDATE, dx, dy),
       location,
@@ skipping 323 matching lines @@
     return;
 
   // Since long press timer has been started, there should be a non-NULL point.
   const GesturePoint* point = GetPointByPointId(0);
   if (!ui::gestures::IsInsideManhattanSquare(point->first_touch_position(),
       event.GetLocation()))
     long_press_timer_->Stop();
 }
 
 }  // namespace ui