Lay groudwork to Closure compile JavaScript

ui/webui/resources/js/parse_html_subset.js

 // Copyright (c) 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.
 
 /**
  * Parse a very small subset of HTML.  This ensures that insecure HTML /
  * javascript cannot be injected into the new tab page.
  * @param {string} s The string to parse.
  * @param {Array.<string>=} opt_extraTags Optional extra allowed tags.
  * @param {Object.<string, function(Node, string):boolean>=} opt_extraAttrs
@@ skipping 19 matching lines @@
     }
   };
 
   /**
    * Whitelist of tag names allowed in parseHtmlSubset.
    * @type {!Array.<string>}
    * @const
    */
   var allowedTags = ['A', 'B', 'STRONG'];
 
-  function merge() {
+  /** @param {...Object} var_args Objects to merge. */
+  function merge(var_args) {
     var clone = {};
     for (var i = 0; i < arguments.length; ++i) {
       if (typeof arguments[i] == 'object') {
         for (var key in arguments[i]) {
           if (arguments[i].hasOwnProperty(key))
             clone[key] = arguments[i][key];
         }
       }
     }
     return clone;
@@ skipping 17 matching lines @@
     if (!attrs.hasOwnProperty(n) || !attrs[n](node, v))
       throw Error(node.tagName + '[' + n + '="' + v + '"] is not supported');
   }
 
   return function(s, opt_extraTags, opt_extraAttrs) {
     var extraTags =
         (opt_extraTags || []).map(function(str) { return str.toUpperCase(); });
     var tags = allowedTags.concat(extraTags);
     var attrs = merge(allowedAttributes, opt_extraAttrs || {});
 
-    var doc = document.implementation.createHTMLDocument('');
+    /** @suppress {missingProperties} */

[arv (Not doing code reviews), 2014/07/16 18:33:03]

Why is this needed?

[Dan Beam, 2014/07/19 02:28:40]

.createHTMLDocument()

[arv (Not doing code reviews), 2014/07/21 18:25:31]

I still don't understand why this refactoring is needed? Is there a bug in the
externs we are using?

[Dan Beam, 2014/07/21 22:30:46]

yes, @suppress => @externs (and added to compiler) here:
https://chromiumcodereview.appspot.com/405743002/

+    function createDoc() {
+      return document.implementation.createHTMLDocument('');
+    }
+
+    var doc = createDoc();
     var r = doc.createRange();
     r.selectNode(doc.body);
     // This does not execute any scripts because the document has no view.
     var df = r.createContextualFragment(s);
     walk(df, function(node) {
       switch (node.nodeType) {
         case Node.ELEMENT_NODE:
           assertElement(tags, node);
           var nodeAttrs = node.attributes;
           for (var i = 0; i < nodeAttrs.length; ++i) {
             assertAttribute(attrs, nodeAttrs[i], node);
           }
           break;
 
         case Node.COMMENT_NODE:
         case Node.DOCUMENT_FRAGMENT_NODE:
         case Node.TEXT_NODE:
           break;
 
         default:
           throw Error('Node type ' + node.nodeType + ' is not supported');
       }
     });
     return df;
   };
 })();