MD History: update iron-list and dependencies for better scroll performance

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 30 matching lines @@
     '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() {
+            // <iron-list>#_maxPages controls the default number of "pages" of
+            // "physical" (i.e. DOM) elements to render. Some of these tests
+            // rely on rendering up to 3 "pages" of items, which was previously
+            // the default, changeed to 2 for performance reasons. TODO(dbeam):
+            // maybe trim down the number of items created in the tests? Or
+            // don't touch <iron-list>'s physical items as much?
+            Array.from(document.querySelectorAll('* /deep/ iron-list')).forEach(
+                function(ironList) { ironList._maxPages = 3; });
+          })
           .then(function() { return md_history.ensureLazyLoaded(); })
           .then(function() {
             $('history-app').queryState_.queryingDisabled = true;
           });
     });
   },
 };
 
 TEST_F('MaterialHistoryBrowserTest', 'BrowserServiceTest', function() {
   md_history.browser_service_test.registerTests();
@@ skipping 94 matching lines @@
       });
     });
   },
 };
 
 TEST_F('MaterialHistoryWithQueryParamTest', 'RoutingTestWithQueryParam',
   function() {
     md_history.history_routing_test_with_query_param.registerTests();
     mocha.run();
 });