MD Settings: Fix scrolling when navigating Forwards from BASIC page.

chrome/test/data/webui/settings/basic_page_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 Suite of tests for the Settings basic page. */
 
 GEN_INCLUDE(['settings_page_browsertest.js']);
 
 /**
  * @constructor
@@ skipping 109 matching lines @@
         // Should be scrolled to the On Startup section.
         assertNotEquals(0, page.scroller.scrollTop);
 
         return new Promise(function(resolve) {
           listenOnce(window, 'popstate', resolve);
           settings.navigateToPreviousRoute();
         });
       }).then(function() {
         // Should be at the top of the page after going Back from the section.
         assertEquals(0, page.scroller.scrollTop);
+
+        return new Promise(function(resolve) {
+          listenOnce(window, 'popstate', resolve);
+          window.history.forward();
+        });
+      }).then(function() {
+        // Should scroll when navigating forwards from the BASIC page.
+        assertNotEquals(0, page.scroller.scrollTop);
       });
     });
 
     test('scroll to section after exiting search', function() {
       var searchManager = new TestSearchManager();
       settings.setSearchManagerForTesting(searchManager);
 
       settings.navigateTo(settings.Route.BASIC,
                           new URLSearchParams(`search=foobar`),
                           /* removeSearch */ false);
@@ skipping 14 matching lines @@
             }
           }, 55);
         });
       });
     });
   });
 
   // Run all registered tests.
   mocha.run();
 });