[Android] Remove the fork of GestureDetector.java

ui/events/gesture_detection/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_GESTURE_DETECTOR_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_
 
+#include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
 #include "ui/events/gesture_detection/velocity_tracker_state.h"
 
 namespace ui {
 
 class MotionEvent;
 
 // Port of GestureDetector.java from Android
 // * platform/frameworks/base/core/java/android/view/GestureDetector.java
@@ skipping 58 matching lines @@
   };
 
   GestureDetector(const Config& config,
                   GestureListener* listener,
                   DoubleTapListener* optional_double_tap_listener);
   ~GestureDetector();
 
   bool OnTouchEvent(const MotionEvent& ev);
 
   void set_doubletap_listener(DoubleTapListener* double_tap_listener) {
+    DCHECK(!is_double_tapping_ || double_tap_listener_);
     double_tap_listener_ = double_tap_listener;
   }
 
   void set_is_longpress_enabled(bool is_longpress_enabled) {
     is_longpress_enabled_ = is_longpress_enabled;
   }
 
   bool is_longpress_enabled() const { return is_longpress_enabled_; }
 
  private:
@@ skipping 41 matching lines @@
 
   // Determines speed during touch scrolling.
   VelocityTrackerState velocity_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureDetector);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_DETECTOR_H_