[polymer] switch comment style

pkg/polymer/example/canonicalization3/test/bad_lib_import_negative_test.dart

 // Copyright (c) 2013, 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.
 
-/** Tests how canonicalization works when using the deployed app. */
+/// Tests how canonicalization works when using the deployed app.
 library canonicalization.bad_lib_import_negative;
 
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
 
 import 'package:canonicalization/a.dart';
 import 'packages/canonicalization/b.dart';
 import 'package:canonicalization/c.dart';
 import 'package:canonicalization/d.dart' as d1;
@@ skipping 14 matching lines @@
     // that's ok.
     expect(b, 0, reason:
       'deploy picks the "package:" url as the canonical url for script tags.');
     expect(c, 2, reason: 'c was always imported with "package:" urls.');
     expect(d1.d, 2, reason: 'both a and b are loaded using package: urls');
 
     // same here
     expect(d2.d, 0, reason: 'both a and b are loaded using package: urls');
   });
 }