MD History: Preload bold Roboto font

chrome/browser/resources/md_history/app.js

 // Copyright 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.
 
 cr.define('md_history', function() {
   var lazyLoadPromise = null;
   function ensureLazyLoaded() {
     if (!lazyLoadPromise) {
       lazyLoadPromise = new Promise(function(resolve, reject) {
         Polymer.Base.importHref(
@@ skipping 129 matching lines @@
 
     // Focus the search field on load. Done here to ensure the history page
     // is rendered before we try to take focus.
     var searchField =
         /** @type {HistoryToolbarElement} */ (this.$.toolbar).searchField;
     if (!searchField.narrow) {
       searchField.getSearchInput().focus();
     }
 
     // Lazily load the remainder of the UI.
-    md_history.ensureLazyLoaded();
+    md_history.ensureLazyLoaded().then(function() {
+      window.requestIdleCallback(function() {
+        document.fonts.load('bold 12px Roboto');
+      });
+    });
   },
 
   /** Overridden from IronScrollTargetBehavior */
   _scrollHandler: function() {
     if (this.scrollTarget)
       this.toolbarShadow_ = this.scrollTarget.scrollTop != 0;
   },
 
   /** @private */
   onCrToolbarMenuPromoClose_: function() {
@@ skipping 230 matching lines @@
             break;
         }
         break;
     }
 
     md_history.BrowserService.getInstance().recordHistogram(
       'History.HistoryPageView', histogramValue, HistoryPageViewHistogram.END
     );
   },
 });