html5lib -- workaround dart2js checked issues

pkg/third_party/html5lib/lib/src/tokenizer.dart

 library tokenizer;
 
 import 'dart:collection';
 import 'dart:math';
 import 'package:html5lib/parser.dart' show HtmlParser;
 import 'package:source_maps/span.dart' show Span, FileSpan;
 import 'constants.dart';
 import 'inputstream.dart';
 import 'token.dart';
 import 'utils.dart';
@@ skipping 41 matching lines @@
   HtmlParser parser;
 
   final Queue<Token> tokenQueue;
 
   /** Holds the token that is currently being processed. */
   Token currentToken;
 
   /**
    * Holds a reference to the method to be invoked for the next parser state.
    */
-  Predicate state;
+  // TODO(jmesserly): the type should be "Predicate" but a dart2js checked mode
+  // bug prevents us from doing that. See http://dartbug.com/12465
+  Function state;
 
   String temporaryBuffer;
 
   int _lastOffset;
 
   // TODO(jmesserly): ideally this would be a LinkedHashMap and we wouldn't add
   // an item until it's ready. But the code doesn't have a clear notion of when
   // it's "done" with the attribute.
   List<TagAttribute> _attributes;
   Set<String> _attributeNames;
@@ skipping 1818 matching lines @@
     }
 
     if (data.length > 0) {
       _addToken(new CharactersToken(data.join()));
     }
     state = dataState;
     return true;
   }
 }