[html5lib] triple slash comment style

pkg/third_party/html5lib/test/parser_feature_test.dart

-/** Additional feature tests that aren't based on test data. */
+/// Additional feature tests that aren't based on test data.
 library parser_feature_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/parser.dart';
 import 'package:html5lib/src/constants.dart';
 import 'package:html5lib/src/treebuilder.dart';
 
 main() {
   test('doctype is cloneable', () {
@@ skipping 269 matching lines @@
     expect((c as Comment).data, 'foo');
     expect(c.text, 'foo');
     expect(e.text, 'bar');
 
     c.text = 'qux';
     expect(c.data, 'qux');
     expect(c.text, 'qux');
     expect(e.text, 'bar');
   });
 }