add initWebComponents

lib/build/mirrors_remover.dart

+// Copyright (c) 2015, 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 web_components.build.mirrors_remover;
+
+import 'dart:async';
+import 'package:barback/barback.dart';
+
+/// Removes `mirror_initializer.dart` and replaces it with
+/// `static_initializer.dart`.
+class MirrorsRemoverTransformer extends Transformer {
+  MirrorsRemoverTransformer();
+  MirrorsRemoverTransformer.asPlugin(BarbackSettings settings);
+
+  bool isPrimary(AssetId id) => id.path == 'lib/src/init.dart';
+
+  @override
+  Future apply(Transform transform) async {
+    String source = await transform.primaryInput.readAsString();
+    source = source.replaceFirst(
+        'mirror_initializer.dart', 'static_initializer.dart');
+    transform.addOutput(
+        new Asset.fromString(transform.primaryInput.id, source));
+  }
+}