Made parse_html_subset pre-compilable.

Moved helper functions and static collections into scoped closure.
These changes:
  - remove pollution of the global namespace
  - avoid the creation of new helper functions each time the parse
    method is called
  - allow this file to be pre-compiled

BUG=121430
TEST=Run unit tests by loading parse_html_subset_test.html


Review URL: http://codereview.chromium.org/10261025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@134746 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/shared/js/parse_html_subset.js

@@ -2,35 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-'use strict';
-
-/**
- * Whitelist of tag names allowed in parseHtmlSubset.
- * @type {[string]}
- */
-var allowedTags = ['A', 'B', 'STRONG'];
-
-/**
- * Parse a very small subset of HTML.
- * @param {string} s The string to parse.
- * @throws {Error} In case of non supported markup.
- * @return {DocumentFragment} A document fragment containing the DOM tree.
- */
-var allowedAttributes = {
-  'href': function(node, value) {
-    // Only allow a[href] starting with http:// and https://
-    return node.tagName == 'A' && (value.indexOf('http://') == 0 ||
-        value.indexOf('https://') == 0);
-  },
-  'target': function(node, value) {
-    // Allow a[target] but reset the value to "".
-    if (node.tagName != 'A')
-      return false;
-    node.setAttribute('target', '');
-    return true;
-  },
-};
-
 /**
  * Parse a very small subset of HTML.  This ensures that insecure HTML /
  * javascript cannot be injected into the new tab page.
@@ -41,7 +12,30 @@ var allowedAttributes = {
  * @throws {Error} In case of non supported markup.
  * @return {DocumentFragment} A document fragment containing the DOM tree.
  */
-function parseHtmlSubset(s, extraTags, extraAttrs) {
+var parseHtmlSubset = (function() {
+  'use strict';
+
+  var allowedAttributes = {
+    'href': function(node, value) {
+      // Only allow a[href] starting with http:// and https://
+      return node.tagName == 'A' && (value.indexOf('http://') == 0 ||
+          value.indexOf('https://') == 0);
+    },
+    'target': function(node, value) {
+      // Allow a[target] but reset the value to "".
+      if (node.tagName != 'A')
+        return false;
+      node.setAttribute('target', '');
+      return true;
+    }
+  };
+
+  /**
+   * Whitelist of tag names allowed in parseHtmlSubset.
+   * @type {[string]}
+   */
+  var allowedTags = ['A', 'B', 'STRONG'];
+
   function merge() {
     var clone = {};
     for (var i = 0; i < arguments.length; ++i) {
@@ -62,43 +56,45 @@ function parseHtmlSubset(s, extraTags, extraAttrs) {
     }
   }
 
-  function assertElement(node) {
+  function assertElement(tags, node) {
     if (tags.indexOf(node.tagName) == -1)
       throw Error(node.tagName + ' is not supported');
   }
 
-  function assertAttribute(attrNode, node) {
+  function assertAttribute(attrs, attrNode, node) {
     var n = attrNode.nodeName;
     var v = attrNode.nodeValue;
     if (!attrs.hasOwnProperty(n) || !attrs[n](node, v))
       throw Error(node.tagName + '[' + n + '="' + v + '"] is not supported');
   }
 
-  var tags = allowedTags.concat(extraTags);
-  var attrs = merge(allowedAttributes, extraAttrs);
+  return function(s, extraTags, extraAttrs) {
+    var tags = allowedTags.concat(extraTags);
+    var attrs = merge(allowedAttributes, extraAttrs);
 
-  var r = document.createRange();
-  r.selectNode(document.body);
-  // This does not execute any scripts.
-  var df = r.createContextualFragment(s);
-  walk(df, function(node) {
-    switch (node.nodeType) {
-      case Node.ELEMENT_NODE:
-        assertElement(node);
-        var attrs = node.attributes;
-        for (var i = 0; i < attrs.length; ++i) {
-          assertAttribute(attrs[i], node);
-        }
-        break;
+    var r = document.createRange();
+    r.selectNode(document.body);
+    // This does not execute any scripts.
+    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;
+        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;
-}
+        default:
+          throw Error('Node type ' + node.nodeType + ' is not supported');
+      }
+    });
+    return df;
+  };
+})();