Adding platform patches to allow custom elements polyfill to work with Shadow DOM.

pkg/custom_element/lib/custom-elements.debug.js

 // Copyright (c) 2012 The Polymer Authors. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //    * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //    * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
@@ skipping 1418 matching lines @@
 // https://github.com/Polymer/platform/blob/master/src/patches-shadowdom-polyfill.js
 // include .host reference
 if (HTMLElement.prototype.createShadowRoot) {
   var originalCreateShadowRoot = HTMLElement.prototype.createShadowRoot;
   HTMLElement.prototype.createShadowRoot = function() {
     var root = originalCreateShadowRoot.call(this);
     root.host = this;
     return root;
   }
 }
+
+
+// Patch to allow custom elements and shadow dom to work together, from:
+// https://github.com/Polymer/platform/blob/master/src/patches-custom-elements.js
+if (window.ShadowDOMPolyfill) {
+  function nop() {};
+
+  // disable shadow dom watching
+  CustomElements.watchShadow = nop;
+  CustomElements.watchAllShadows = nop;
+
+  // ensure wrapped inputs for these functions
+  var fns = ['upgradeAll', 'upgradeSubtree', 'observeDocument',
+      'upgradeDocument'];
+
+  // cache originals
+  var original = {};
+  fns.forEach(function(fn) {
+    original[fn] = CustomElements[fn];
+  });
+
+  // override
+  fns.forEach(function(fn) {
+    CustomElements[fn] = function(inNode) {
+      return original[fn](ShadowDOMPolyfill.wrapIfNeeded(inNode));
+    };
+  });
+}
+
 })();