Move DomProxyMixin to this package

lib/src/init.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.src.init;
 
 import 'dart:async';
 import 'package:initialize/initialize.dart' show InitializerFilter;
 import 'package:web_components/web_components.dart';
 import 'mirror_initializer.dart' as init;
 export 'mirror_initializer.dart' show deployMode;
 
 /// Performs html import aware initialization by crawling all imported documents
 /// and initializing any script tags which appear in them.
 ///
 /// By default, this will run all [HtmlImport] initializers, followed in a 2nd
 /// phase by all [CustomElement] and [CustomElementProxy] initializers. Then,
 /// unless [initAll] is [false], it will run all remaining initializers.
 ///
 /// If a [typeFilter] or [customFilter] are supplied, only one phase is ran
 /// with the supplied filters.
 Future initWebComponents({List<Type> typeFilter, InitializerFilter customFilter,
     bool initAll: true}) {
   if (typeFilter != null || customFilter != null) {
     return init.run(typeFilter: typeFilter, customFilter: customFilter);
   } else {
-    return init.run(typeFilter: [HtmlImport])
-      .then((_) => init.run(typeFilter: [CustomElement, CustomElementProxy]))
-      .then((_) => initAll ? init.run() : null);
+    return init
+        .run(typeFilter: [HtmlImport])
+        .then((_) => init.run(typeFilter: [CustomElement, CustomElementProxy]))
+        .then((_) => initAll ? init.run() : null);
   }
 }