Implement UIEvent.sourceDevice

Source/core/events/UIEvent.idl

 /*
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 // https://w3c.github.io/uievents/#interface-UIEvent
 
 [
     Constructor(DOMString type, optional UIEventInit eventInitDict)
 ] interface UIEvent : Event {
     readonly attribute Window? view;
     readonly attribute long detail;
+    [RuntimeEnabled=InputDevice] readonly attribute InputDevice? sourceDevice;
 
     // https://w3c.github.io/uievents/#idl-interface-UIEvent-initializers
     // TODO(philipj): None of the initUIEvent() arguments should be optional.
     void initUIEvent([Default=Undefined] optional DOMString type,
                                     [Default=Undefined] optional boolean bubbles,
                                     [Default=Undefined] optional boolean cancelable,
                                     [Default=Undefined] optional Window? view,
                                     [Default=Undefined] optional long detail);
 
     // Non-standard
     [MeasureAs=UIEventLayerX] readonly attribute long layerX;
     [MeasureAs=UIEventLayerY] readonly attribute long layerY;
     [MeasureAs=UIEventPageX] readonly attribute long pageX;
     [MeasureAs=UIEventPageY] readonly attribute long pageY;
 
     // FIXME: these belong on the KeyboardEvent interface
     [MeasureAs=UIEventCharCode] readonly attribute long charCode;
     [MeasureAs=UIEventKeyCode] readonly attribute long keyCode;
     [MeasureAs=UIEventWhich] readonly attribute long which;
 };