MD History: Lazily load element files which are not needed for first paint

chrome/test/data/webui/md_history/md_history_browsertest.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview Test suite for the Material Design history page.
  */
 
 var ROOT_PATH = '../../../../../';
 
@@ skipping 29 matching lines @@
     'history_synced_tabs_test.js',
     'history_toolbar_test.js',
   ]),
 
   /** @override */
   setUp: function() {
     PolymerTest.prototype.setUp.call(this);
 
     suiteSetup(function() {
       // Wait for the top-level app element to be upgraded.
-      return waitForAppUpgrade().then(function() {
-        $('history-app').queryState_.queryingDisabled = true;
-      });
+      return waitForAppUpgrade()
+          .then(function() { return md_history.ensureLazyLoaded(); })
+          .then(function() {
+            $('history-app').queryState_.queryingDisabled = true;
+          });
     });
   },
 };
 
 TEST_F('MaterialHistoryBrowserTest', 'BrowserServiceTest', function() {
   md_history.browser_service_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'DrawerTest', function() {
@@ skipping 67 matching lines @@
 function MaterialHistoryWithQueryParamTest() {}
 
 MaterialHistoryWithQueryParamTest.prototype = {
   __proto__: MaterialHistoryBrowserTest.prototype,
 
   browsePreload: 'chrome://history?q=query',
 
   /** @override */
   setUp: function() {
     PolymerTest.prototype.setUp.call(this);
+    // This message handler needs to be registered before the test since the
+    // query can happen immediately after the element is upgraded. However,
+    // since there may be a delay as well, the test might check the global var
+    // too early as well. In this case the test will have overtaken the
+    // callback.
+    registerMessageCallback('queryHistory', this, function (info) {
+      window.historyQueryInfo = info;
+    });
 
     suiteSetup(function() {
-      // This message handler needs to be registered before the test since the
-      // query can happen immediately after the element is upgraded. However,
-      // since there may be a delay as well, the test might check the global var
-      // too early as well. In this case the test will have overtaken the
-      // callback.
-      registerMessageCallback('queryHistory', this, function (info) {
-        window.historyQueryInfo = info;
+      // Wait for the top-level app element to be upgraded.
+      return waitForAppUpgrade().then(function() {
+        md_history.ensureLazyLoaded();
       });
-
-      // Wait for the top-level app element to be upgraded.
-      return waitForAppUpgrade();
     });
   },
 };
 
 TEST_F('MaterialHistoryWithQueryParamTest', 'RoutingTestWithQueryParam',
   function() {
     md_history.history_routing_test_with_query_param.registerTests();
     mocha.run();
 });