Remove most of the loading delay for warning icon.

ui/login/account_picker/user_pod_template.js

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function() {
   "use strict";
 
-  var START_LOADING_DELAY = 1000;
-
-  function doLazyLoad() {
-    function lazyLoadUrl(url) {
-      var link = document.createElement('link');
-      link.rel = 'import';
-      link.href = url;
-      document.body.appendChild(link);
-    }
-
-    lazyLoadUrl('chrome://resources/polymer/v1_0/iron-icons/iron-icons.html');
-    lazyLoadUrl(
-        'chrome://resources/polymer/v1_0/paper-button/paper-button.html');
-  }
+  var RESOURCES_TO_LOAD = [
+    'chrome://resources/polymer/v1_0/iron-icons/iron-icons.html',
+    'chrome://resources/polymer/v1_0/paper-button/paper-button.html'
+  ];
+  /* const */ var IDLE_TIMEOUT_MS = 200;
 
   window.addEventListener('load', function() {
-    setTimeout(doLazyLoad, START_LOADING_DELAY);
+    // The user pod template gets cloned shortly after the load event to make
+    // the actual user pods. It then takes a few update cycles to style these
+    // elements. Loading polymer will block the DOM, so we try to load polymer
+    // after the user pods have been cloned and styled.
+    requestIdleCallback(function() {
+      for (var resourceUrl of RESOURCES_TO_LOAD) {
+        var link = document.createElement('link');
+        link.rel = 'import';
+        link.href = resourceUrl;
+        document.head.appendChild(link);
+      }
+    }, { timeout: IDLE_TIMEOUT_MS });
   });
 })();