introduce web_components pkg for consolidated polyfills

pkg/shadow_dom/lib/src/platform/platform-init.js

Index: pkg/shadow_dom/lib/src/platform/platform-init.js
diff --git a/pkg/shadow_dom/lib/src/platform/platform-init.js b/pkg/shadow_dom/lib/src/platform/platform-init.js
deleted file mode 100644
index 4e83afc8c5fafb541d0e44d97fbd3621ddba5040..0000000000000000000000000000000000000000
--- a/pkg/shadow_dom/lib/src/platform/platform-init.js
+++ /dev/null
@@ -1,5 +0,0 @@
-// 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.
-
-var Platform = {};