use shared code transformer, update web_components to remove .map and .concat files

pkg/polymer/test/build/remove_sourcemap_comment_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.
-
-library polymer.test.build.remove_sourcemap_comment_test;
-
-import 'package:barback/barback.dart';
-import 'package:polymer/src/build/remove_sourcemap_comment.dart';
-import 'package:unittest/compact_vm_config.dart';
-import 'package:unittest/unittest.dart';
-import 'common.dart';
-
-final phases = [[new RemoveSourcemapComment.asPlugin(
-    new BarbackSettings({}, BarbackMode.RELEASE))]];
-
-void main() {
-  useCompactVMConfiguration();
-
-  testPhases('removes sourcemap comments', phases, {
-      'a|web/test.js': '''
-          var i = 0;
-          //# sourceMappingURL=*.map''',
-  }, {
-      'a|web/test.js': '''
-          var i = 0;''',
-  });
-}