Adding an easy way to allow inline style attributes through sanitization

tools/dom/src/NodeValidatorBuilder.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.dom.html;
 
 
 /**
  * Class which helps construct standard node validation policies.
  *
@@ skipping 92 matching lines @@
    * * OL
    * * P
    * * SPAN
    * * UL
    */
   void allowTextElements() {
     add(new _SimpleNodeValidator.allowTextElements());
   }
 
   /**
+   * Allow inline styles on elements.
+   *
+   * If [tagName] is not specified then this allows inline styles on all
+   * elements. Otherwise tagName limits the styles to the specified elements.
+   */
+  void allowInlineStyles({String tagName}) {
+    if (tagName == null) {
+      tagName = '*';
+    } else {
+      tagName = tagName.toUpperCase();
+    }
+    add(new _SimpleNodeValidator(null, allowedAttributes: ['$tagName::style']));
+  }
+
+  /**
    * Allow common safe HTML5 elements and attributes.
    *
    * This list is based off of the Caja whitelists at:
    * https://code.google.com/p/google-caja/wiki/CajaWhitelists.
    *
    * Common things which are not allowed are script elements, style attributes
    * and any script handlers.
    */
   void allowHtml5({UriPolicy uriPolicy}) {
     add(new _Html5NodeValidator(uriPolicy: uriPolicy));
@@ skipping 321 matching lines @@
     return false;
   }
 
   bool allowsAttribute(Element element, String attributeName, String value) {
     if (attributeName == 'is' || attributeName.startsWith('on')) {
       return false;
     }
     return allowsElement(element);
   }
 }