update polymer js to 0.4.0

pkg/template_binding/lib/js/microtask.js

Index: pkg/template_binding/lib/js/microtask.js
diff --git a/pkg/template_binding/lib/js/microtask.js b/pkg/template_binding/lib/js/microtask.js
new file mode 100644
index 0000000000000000000000000000000000000000..827f2fe221868115734a37c6e26a58ee5883c4d8
--- /dev/null
+++ b/pkg/template_binding/lib/js/microtask.js
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
+ * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
+ * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
+ * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
+ * Code distributed by Google as part of the polymer project is also
+ * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
+ */
+
+(function(scope) {
+
+var iterations = 0;
+var callbacks = [];
+var twiddle = document.createTextNode('');
+
+function endOfMicrotask(callback) {
+  twiddle.textContent = iterations++;
+  callbacks.push(callback);
+}
+
+function atEndOfMicrotask() {
+  while (callbacks.length) {
+    callbacks.shift()();
+  }
+}
+
+new (window.MutationObserver || JsMutationObserver)(atEndOfMicrotask)
+  .observe(twiddle, {characterData: true})
+  ;
+
+// exports
+
+scope.endOfMicrotask = endOfMicrotask;
+
+})(Platform);
+