Merge pull request #581 from kevmoo/polymer

lib/safe_html.dart

 // Copyright (c) 2011, 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.
 
 // TODO(sigmund): move this library to a shared package? or make part of
 // dart:html?
 library polymer.safe_html;
 
 /** Declares a string that is a well-formed HTML fragment. */
 class SafeHtml {
 
   /** Underlying html string. */
-  String _html;
+  final String _html;
 
   // TODO(sigmund): provide a constructor that does html validation
   SafeHtml.unsafe(this._html);
 
   String toString() => _html;
 
   operator ==(other) => other is SafeHtml && _html == other._html;
   int get hashCode => _html.hashCode;
 }
 
 /**
  * Declares a string that is safe to use in a Uri attribute, such as `<a href=`,
  * to avoid cross-site scripting (XSS) attacks.
  */
 class SafeUri {
-  String _uri;
+  final String _uri;
 
   // TODO(sigmund): provide a constructor that takes or creates a Uri and
   // validates that it is safe (not a javascript: scheme, for example)
   SafeUri.unsafe(this._uri);
 
   String toString() => _uri;
 
   operator ==(other) => other is SafeUri && _uri == other._uri;
   int get hashCode => _uri.hashCode;
 }