MD Settings: Preserve search URL param in subpages.

chrome/test/data/webui/settings/settings_ui_browsertest.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.
 
 /** @fileoverview Suite of tests for the Settings layout. */
 
 GEN_INCLUDE(['settings_page_browsertest.js']);
 
 /**
  * @constructor
@@ skipping 98 matching lines @@
       // Check that all values are updated in unison.
       assertFalse(menu.advancedOpened);
       assertFalse(ui.advancedOpened_);
       assertFalse(main.advancedToggleExpanded);
     });
 
     test('URL initiated search propagates to search box', function() {
       toolbar = /** @type {!CrToolbarElement} */ (ui.$$('cr-toolbar'));
       var searchField = /** @type {CrToolbarSearchFieldElement} */ (
           toolbar.getSearchField());
+      assertEquals('', searchField.getSearchInput().bindValue);
 
       var query = 'foo';
       settings.navigateTo(
           settings.Route.BASIC, new URLSearchParams(`search=${query}`));
       assertEquals(query, searchField.getSearchInput().bindValue);
-
-      settings.navigateTo(settings.Route.BASIC);
-      assertEquals('', searchField.getSearchInput().bindValue);
     });
 
     test('search box initiated search propagates to URL', function() {
-      assertFalse(settings.getQueryParameters().has('search'));
       var searchField = /** @type {CrToolbarSearchFieldElement} */ (
           toolbar.getSearchField());
+
+      settings.navigateTo(
+          settings.Route.BASIC, /* dynamicParams */ null,
+          /* removeSearch */ true);
+      assertEquals('', searchField.getSearchInput().bindValue);
+      assertFalse(settings.getQueryParameters().has('search'));
+
       var value = 'GOOG';
       searchField.setValue(value);
       assertEquals(value, settings.getQueryParameters().get('search'));
     });
 
      test('whitespace only search query is ignored', function() {
       toolbar = /** @type {!CrToolbarElement} */ (ui.$$('cr-toolbar'));
       var searchField = /** @type {CrToolbarSearchFieldElement} */ (
           toolbar.getSearchField());
       searchField.setValue('    ');
       var urlParams = settings.getQueryParameters();
       assertFalse(urlParams.has('search'));
 
       searchField.setValue('   foo');
       urlParams = settings.getQueryParameters();
       assertEquals('foo', urlParams.get('search'));
 
       searchField.setValue('   foo ');
       urlParams = settings.getQueryParameters();
       assertEquals('foo ', urlParams.get('search'));
 
       searchField.setValue('   ');
       urlParams = settings.getQueryParameters();
       assertFalse(urlParams.has('search'));
     });
   });
 
   mocha.run();
 });