MD Settings: Ignore whitespace only search queries.

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 107 matching lines @@
           toolbar.getSearchField());
 
       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('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'));
+    });
   });
 
   mocha.run();
 });