[Android] Remove the fork of GestureDetector.java

ui/events/gesture_detection/gesture_detector.cc

 // 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.
 
 #include "ui/events/gesture_detection/gesture_detector.h"
 
 #include <cmath>
 
 #include "base/timer/timer.h"
 #include "ui/events/gesture_detection/motion_event.h"
@@ skipping 246 matching lines @@
 
     case MotionEvent::ACTION_MOVE:
       if (in_longpress_)
         break;
 
       {
         const float scroll_x = last_focus_x_ - focus_x;
         const float scroll_y = last_focus_y_ - focus_y;
         if (is_double_tapping_) {
           // Give the move events of the double-tap.
+          DCHECK(double_tap_listener_);
           handled |= double_tap_listener_->OnDoubleTapEvent(ev);
         } else if (always_in_tap_region_) {
           const int delta_x = static_cast<int>(focus_x - down_focus_x_);
           const int delta_y = static_cast<int>(focus_y - down_focus_y_);
           int distance = (delta_x * delta_x) + (delta_y * delta_y);
           if (distance > touch_slop_square_) {
             handled = listener_->OnScroll(
                 *current_down_event_, ev, scroll_x, scroll_y);
             last_focus_x_ = focus_x;
             last_focus_y_ = focus_y;
             always_in_tap_region_ = false;
             timeout_handler_->Stop();
           }
           if (distance > double_tap_touch_slop_square_)
             always_in_bigger_tap_region_ = false;
         } else if ((std::abs(scroll_x) >= 1) || (std::abs(scroll_y) >= 1)) {
           handled =
               listener_->OnScroll(*current_down_event_, ev, scroll_x, scroll_y);
           last_focus_x_ = focus_x;
           last_focus_y_ = focus_y;
         }
       }
       break;
 
     case MotionEvent::ACTION_UP:
       still_down_ = false;
       {
         if (is_double_tapping_) {
           // Finally, give the up event of the double-tap.
+          DCHECK(double_tap_listener_);
           handled |= double_tap_listener_->OnDoubleTapEvent(ev);
         } else if (in_longpress_) {
           timeout_handler_->StopTimeout(TAP);
           in_longpress_ = false;
         } else if (always_in_tap_region_) {
           handled = listener_->OnSingleTapUp(ev);
           if (defer_confirm_single_tap_ && double_tap_listener_ != NULL) {
             double_tap_listener_->OnSingleTapConfirmed(ev);
           }
         } else {
@@ skipping 92 matching lines @@
   if (second_down.GetEventTime() - first_up.GetEventTime() >
       double_tap_timeout_)
     return false;
 
   int delta_x = static_cast<int>(first_down.GetX() - second_down.GetX());
   int delta_y = static_cast<int>(first_down.GetY() - second_down.GetY());
   return (delta_x * delta_x + delta_y * delta_y < double_tap_slop_square_);
 }
 
 }  // namespace ui