Implement ShadowRoot.delegatesFocus 1/4 (focus navigation)

Source/core/dom/shadow/ShadowRoot.idl

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 18 matching lines @@
 interface ShadowRoot : DocumentFragment {
     Selection? getSelection();
     // TODO(philipj): The x and y arguments should be of type double.
     Element? elementFromPoint(long x, long y);
     sequence<Element> elementsFromPoint(long x, long y);
     readonly attribute Element? activeElement;
     readonly attribute Element host;
     [ImplementedAs=olderShadowRootForBindings] readonly attribute ShadowRoot? olderShadowRoot;
     [TreatNullAs=NullString, CustomElementCallbacks, RaisesException=Setter] attribute DOMString innerHTML;
     readonly attribute StyleSheetList styleSheets;
+    [RuntimeEnabled=ShadowRootDelegatesFocus] readonly attribute boolean delegatesFocus;
 
     // TODO(philipj): The spec does not override cloneNode() on the ShadowRoot
     // interface. Here, it's used to implement "Invoking the cloneNode() method
     // on a ShadowRoot instance must always throw a DATA_CLONE_ERR exception" as
     // Node.cloneNode() does not have [RaisesException].
     [RaisesException] Node cloneNode([Default=Undefined] optional boolean deep);
 };