Made Text#assignedSlot and Element#assignedSlot nullable.

third_party/WebKit/Source/core/dom/Text.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://dom.spec.whatwg.org/#interface-text
 
 [
     Constructor(optional DOMString data = ""),
     ConstructorCallWith=Document,
 ] interface Text : CharacterData {
     [NewObject, DoNotTestNewObject, RaisesException] Text splitText(unsigned long offset);
     [MeasureAs=TextWholeText] readonly attribute DOMString wholeText;
 
-    // Shadow DOM
-    // https://w3c.github.io/webcomponents/spec/shadow/#extensions-to-text-interface
+    // Mixin Slotable
+    // https://dom.spec.whatwg.org/#mixin-slotable
+    [ImplementedAs=assignedSlotForBinding] readonly attribute HTMLSlotElement? assignedSlot;
+
     NodeList getDestinationInsertionPoints();

[foolip, 2016/12/12 11:33:48]

Add back Shadow DOM + link

-    [ImplementedAs=assignedSlotForBinding] readonly attribute HTMLSlotElement assignedSlot;
 };