The parameter of the tester should have spaces in assert_selection()

third_party/WebKit/LayoutTests/editing/assert_selection.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.
 
 'use strict';
 
 // This file provides |assert_selection(sample, tester, expectedText)| assertion
 // to W3C test harness to write editing test cases easier.
 //
 // |sample| is an HTML fragment text which is inserted as |innerHTML|. It should
@@ skipping 643 matching lines @@
 function assertSelection(
     inputText, tester, expectedText, opt_description = '') {
   /** @type {string} */
   const description =
       opt_description === '' ? assembleDescription() : opt_description;
   checkExpectedText(expectedText);
   const sample = new Sample(inputText);
   if (typeof(tester) === 'function') {
     tester.call(window, sample.selection);
   } else if (typeof(tester) === 'string') {
-    const strings = tester.split(' ');
+    const strings = tester.split(/ (.+)/);
     sample.document.execCommand(strings[0], false, strings[1]);
   } else {
     throw new Error(`Invalid tester: ${tester}`);
   }
   /** @type {string} */
   const actualText = sample.serialize();
   // We keep sample HTML when assertion is false for ease of debugging test
   // case.
   if (actualText === expectedText) {
     sample.remove();
     return;
   }
   throw new Error(`${description}\n` +
     `\t expected ${expectedText},\n` +
     `\t but got  ${actualText},\n` +
     `\t sameupto ${commonPrefixOf(expectedText, actualText)}`);
 }
 
 // Export symbols
 window.Sample = Sample;
 window.assert_selection = assertSelection;
 })();