Changed UnsupportedOperationException to UnsupportedError

test/tokenizer_test.dart

 library tokenizer_test;
 
 // Note: mirrors used to match the getattr usage in the original test
 import 'dart:io';
 import 'dart:json';
 import 'dart:mirrors';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/vm_config.dart';
 import 'package:html5lib/src/char_encodings.dart';
 import 'package:html5lib/src/constants.dart' as constants;
@@ skipping 55 matching lines @@
 
     // Note: we can't get a closure of the state method. However, we can
     // create a new closure to invoke it via mirrors.
     var mtok = reflect(tokenizer);
     tokenizer.state = () => mtok.invoke(_state, const []).value.reflectee;
 
     if (_lastStartTag != null) {
       tokenizer.currentToken = new StartTagToken(_lastStartTag);
     }
 
-    while (tokenizer.hasNext()) {
+    while (tokenizer.hasNext) {
       var token = tokenizer.next();
       switch (token.kind) {
         case TokenKind.characters:
           processCharacters(token);
           break;
         case TokenKind.spaceCharacters:
           processSpaceCharacters(token);
           break;
         case TokenKind.startTag:
           processStartTag(token);
@@ skipping 208 matching lines @@
             test(testInfo["description"], () {
               testInfo["initialState"] = camelCase(initialState);
               runTokenizerTest(testInfo);
             });
           }
         }
       });
     }
   });
 }