fix accidental breaking changes in html5lib, deprecate instead

pkg/third_party/html5lib/lib/dom.dart

 /**
  * A simple tree API that results from parsing html. Intended to be compatible
  * with dart:html, but right now it resembles the classic JS DOM.
  */
 library dom;
 
 import 'dart:collection';
 import 'package:source_maps/span.dart' show FileSpan;
 
 import 'src/constants.dart';
@@ skipping 136 matching lines @@
   /**
    * Return a shallow copy of the current node i.e. a node with the same
    * name and attributes but with no parent or child nodes.
    */
   Node clone();
 
   String get namespace => null;
 
   int get nodeType;
 
+  /** *Deprecated* use [text], [Text.data] or [Comment.data]. */
+  @deprecated String get value => null;
+
+  /** *Deprecated* use [nodeType]. */
+  @deprecated int get $dom_nodeType => nodeType;
+
   String get outerHtml {
     var str = new StringBuffer();
     _addOuterHtml(str);
     return str.toString();
   }
 
   String get innerHtml {
     var str = new StringBuffer();
     _addInnerHtml(str);
     return str.toString();
@@ skipping 259 matching lines @@
   }
 
   DocumentType clone() => new DocumentType(tagName, publicId, systemId);
 }
 
 class Text extends Node {
   String data;
 
   Text(this.data) : super(null);
 
+  /** *Deprecated* use [data]. */
+  @deprecated String get value => data;
+  @deprecated set value(String x) { data = x; }
+
   int get nodeType => Node.TEXT_NODE;
 
   String toString() => '"$data"';
 
   void _addOuterHtml(StringBuffer str) {
     // Don't escape text for certain elements, notably <script>.
     if (rcdataElements.contains(parent.tagName) ||
         parent.tagName == 'plaintext') {
       str.write(data);
     } else {
@@ skipping 461 matching lines @@
 
 class _ConcatTextVisitor extends TreeVisitor {
   final _str = new StringBuffer();
 
   String toString() => _str.toString();
 
   visitText(Text node) {
     _str.write(node.data);
   }
 }