Sync HTML element interfaces S-V with the spec

Source/core/events/Event.idl

 /*
  * Copyright (C) 2006, 2007, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * 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,
@@ skipping 34 matching lines @@
 
     // FIXME: Implement the isTrusted attribute. crbug.com/334015
     // [Unforgeable] readonly attribute boolean isTrusted;
     readonly attribute DOMTimeStamp timeStamp;
 
     // FIXME: initEvent()'s arguments should not be optional.
     void initEvent([Default=Undefined] optional DOMString eventTypeArg,
                    [Default=Undefined] optional boolean canBubbleArg,
                    [Default=Undefined] optional boolean cancelableArg);
 
+    // Shadow DOM
+    // https://w3c.github.io/webcomponents/spec/shadow/#extensions-to-event-interface
+    [MeasureAs=EventPath] readonly attribute EventTarget[] path;
+
     // Non-standard APIs
     const unsigned short MOUSEDOWN = 1;
     const unsigned short MOUSEUP   = 2;
     const unsigned short MOUSEOVER = 4;
     const unsigned short MOUSEOUT  = 8;
     const unsigned short MOUSEMOVE = 16;
     const unsigned short MOUSEDRAG = 32;
     const unsigned short CLICK     = 64;
     const unsigned short DBLCLICK  = 128;
     const unsigned short KEYDOWN   = 256;
     const unsigned short KEYUP     = 512;
     const unsigned short KEYPRESS  = 1024;
     const unsigned short DRAGDROP  = 2048;
     const unsigned short FOCUS     = 4096;
     const unsigned short BLUR      = 8192;
     const unsigned short SELECT    = 16384;
     const unsigned short CHANGE    = 32768;
     [MeasureAs=EventSrcElement] readonly attribute EventTarget srcElement;
     [MeasureAs=EventReturnValue, CallWith=ExecutionContext, ImplementedAs=legacyReturnValue] attribute boolean returnValue;
     [MeasureAs=EventCancelBubble] attribute boolean cancelBubble;
-    [MeasureAs=EventPath] readonly attribute EventTarget[] path;
 };