Implementing document.setRootScroller API for main thread scrolling.

third_party/WebKit/Source/core/dom/Document.idl

 /*
  * Copyright (C) 2006, 2007, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006, 2007 Samuel Weinig <sam@webkit.org>
  *
  * 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,
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     [NewObject, RaisesException, MeasureAs=DocumentCreateAttributeNS] Attr createAttributeNS(DOMString? namespaceURI, DOMString qualifiedName);
 
     [NewObject, RaisesException, CallWith=ExecutionContext] Event createEvent(DOMString eventType);
 
     [NewObject] Range createRange();
 
     // NodeFilter.SHOW_ALL = 0xFFFFFFFF
     [NewObject] NodeIterator createNodeIterator(Node root, optional unsigned long whatToShow = 0xFFFFFFFF, optional NodeFilter? filter = null);
     [NewObject] TreeWalker createTreeWalker(Node root, optional unsigned long whatToShow = 0xFFFFFFFF, optional NodeFilter? filter = null);
 
+    // NonDocumentRootScroller (https://github.com/bokand/NonDocumentRootScroller)
+    [RuntimeEnabled=SetRootScroller, RaisesException] void setRootScroller (Element element);
+    [RuntimeEnabled=SetRootScroller] readonly attribute Element? rootScroller;
+
+
     // FIXME: CDATASection has been removed from the spec. crbug.com/437205
     [RaisesException, MeasureAs=DocumentCreateCDATASection] CDATASection createCDATASection(DOMString data);
 
     // FIXME: xmlEncoding/xmlVersion/xmlStandalone have been removed from the spec.
     [MeasureAs=DocumentXMLEncoding] readonly attribute DOMString? xmlEncoding;
     [RaisesException=Setter, MeasureAs=DocumentXMLVersion] attribute DOMString? xmlVersion;
     [RaisesException=Setter, MeasureAs=DocumentXMLStandalone] attribute boolean xmlStandalone;
 
     // HTML
     // https://html.spec.whatwg.org/#the-document-object
@@ skipping 128 matching lines @@
     [RuntimeEnabled=ExperimentalContentSecurityPolicyFeatures] attribute EventHandler onsecuritypolicyviolation;
     attribute EventHandler onselectionchange;
     attribute EventHandler onselectstart;
     attribute EventHandler onwheel;
 };
 
 Document implements GlobalEventHandlers;
 Document implements ParentNode;
 Document implements NonElementParentNode;
 Document implements DocumentOrShadowRoot;