Use element.createShadowRoot since WebKitShadowRoot is deprecated.

chrome/renderer/resources/extensions/searchbox_api.js

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var chrome;
 if (!chrome)
   chrome = {};
 if (!chrome.searchBox) {
   chrome.searchBox = new function() {
     var safeObjects = {};
     chrome.searchBoxOnWindowReady = function() {
       // |searchBoxOnWindowReady| is used for initializing window context and
       // should be called only once per context.
-      safeObjects.ShadowRoot = window.WebKitShadowRoot;
+      safeObjects.createShadowRoot = Element.prototype.webkitCreateShadowRoot;
       safeObjects.defineProperty = Object.defineProperty;
       delete window.chrome.searchBoxOnWindowReady;
     };
 
     // =========================================================================
     //                                  Constants
     // =========================================================================
     var MAX_CLIENT_SUGGESTIONS_TO_DEDUPE = 6;
     var MAX_ALLOWED_DEDUPE_ATTEMPTS = 5;
 
@@ skipping 26 matching lines @@
     native function SetQuerySuggestionFromAutocompleteResult();
     native function SetQuery();
     native function SetQueryFromAutocompleteResult();
     native function Show();
     native function StartCapturingKeyStrokes();
     native function StopCapturingKeyStrokes();
 
     // Returns the |restrictedText| wrapped in a ShadowDOM.
     function SafeWrap(restrictedText) {
       var node = document.createElement('div');
-      var nodeShadow = new safeObjects.ShadowRoot(node);
+      var nodeShadow = safeObjects.createShadowRoot.apply(node);
       nodeShadow.applyAuthorStyles = true;
       nodeShadow.innerHTML =
           '<div style="width:700px!important;' +
           '            height:22px!important;' +
           '            font-family:\'' + GetFont() + '\',\'Arial\'!important;' +
           '            overflow:hidden!important;' +
           '            text-overflow:ellipsis!important">' +
           '  <nobr>' + restrictedText + '</nobr>' +
           '</div>';
       safeObjects.defineProperty(node, 'webkitShadowRoot', { value: null });
@@ skipping 160 matching lines @@
     this.onchange = null;
     this.onsubmit = null;
     this.oncancel = null;
     this.onresize = null;
     this.onautocompleteresults = null;
     this.onkeypress = null;
     this.onkeycapturechange = null;
     this.oncontextchange = null;
   };
 }