Import Polymer 0.8 and several key elements.

third_party/polymer/v0_8/components/polymer/src/lib/async.html

Index: third_party/polymer/v0_8/components/polymer/src/lib/async.html
diff --git a/third_party/polymer/v0_8/components/polymer/src/lib/async.html b/third_party/polymer/v0_8/components/polymer/src/lib/async.html
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+<!--
+@license
+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
+-->
+<script>
+
+Polymer.Async = (function() {
+  
+  var currVal = 0;
+  var lastVal = 0;
+  var callbacks = [];
+  var twiddle = document.createTextNode('');
+
+  function runAsync(callback, waitTime) {
+    if (waitTime > 0) {
+      return ~setTimeout(callback, waitTime);
+    } else {
+      twiddle.textContent = currVal++;
+      callbacks.push(callback);
+      return currVal - 1;
+    }
+  }
+
+  function cancelAsync(handle) {
+    if (handle < 0) {
+      clearTimeout(~handle);
+    } else {
+      var idx = handle - lastVal;
+      if (idx >= 0) {
+        if (!callbacks[idx]) {
+          throw 'invalid async handle: ' + handle;
+        }
+        callbacks[idx] = null;
+      }
+    }
+  }
+
+  function atEndOfMicrotask() {
+    var len = callbacks.length;
+    for (var i=0; i<len; i++) {
+      var cb = callbacks[i];
+      if (cb) {
+        cb();
+      }
+    }
+    callbacks.splice(0, len);
+    lastVal += len;
+  }
+
+  new (window.MutationObserver || JsMutationObserver)(atEndOfMicrotask)
+    .observe(twiddle, {characterData: true})
+    ;
+  
+  // exports 
+
+  return {
+    run: runAsync,
+    cancel: cancelAsync
+  };
+  
+})();
+
+</script>