Don't expose WebKitShadowRoot constructor.

Source/core/dom/shadow/ShadowRoot.idl

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
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  * modification, are permitted provided that the following conditions are
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-[
-    NoInterfaceObject
-] interface ShadowRoot : DocumentFragment {
+interface ShadowRoot : DocumentFragment {
     readonly attribute Element activeElement;
 
     [ImplementedAs=olderShadowRootForBindings] readonly attribute ShadowRoot olderShadowRoot;
 
     [TreatNullAs=NullString, CustomElementCallbacks, PerWorldBindings, ActivityLogging=SetterForIsolatedWorlds, RaisesException=Setter] attribute DOMString innerHTML;
 
     [RaisesException] Node cloneNode([Default=Undefined] optional boolean deep);
     Selection getSelection();
     Element getElementById([Default=Undefined] optional DOMString elementId);
     HTMLCollection getElementsByClassName([Default=Undefined] optional DOMString className);
     HTMLCollection getElementsByTagName([Default=Undefined] optional DOMString tagName);
     HTMLCollection getElementsByTagNameNS([TreatNullAs=NullString,Default=Undefined] optional DOMString namespaceURI,
                                           [Default=Undefined] optional DOMString localName);
 
     Element elementFromPoint([Default=Undefined] optional long x,
                              [Default=Undefined] optional long y);
 
     readonly attribute StyleSheetList styleSheets;
     readonly attribute Element host;
 };