[Editing][CodeHealth] Allow assert_selection have no anchor sample text.

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 444 matching lines @@
     }
     this.serializeChildren(element);
     this.emit(`</${tagName}>`);
   }
 
   /**
    * @public
    * @param {!HTMLDocument} document
    */
   serialize(document) {
-    if (this.selection_.isNone)
-      return document.body.firstChild.outerHTML;
     this.serializeChildren(document.body);
     return this.strings_.join('');
   }
 
   /**
    * @private
    * @param {!HTMLElement} element
    */
   serializeChildren(element) {
     /** @type {!Array<!Node>} */
@@ skipping 50 matching lines @@
   /** @return {!Selection} */
   get selection() { return this.selection_; }
 
   /**
    * @private
    * @param {string} sampleText
    */
   load(sampleText) {
     const anchorMarker = sampleText.indexOf('^');
     const focusMarker = sampleText.indexOf('|');
-    if (focusMarker < 0) {
+    if (focusMarker < 0 && anchorMarker >= 0) {
       throw new Error(`You should specify caret position in "${sampleText}".`);
     }
     if (focusMarker != sampleText.lastIndexOf('|')) {
       throw new Error(
           `You should have at least one focus marker "|" in "${sampleText}".`);
     }
     if (anchorMarker != sampleText.lastIndexOf('^')) {
       throw new Error(
           `You should have at most one anchor marker "^" in "${sampleText}".`);
     }
@@ skipping 104 matching lines @@
   // case.
   if (actualText === expectedText)
     sample.remove();
   assert_equals(actualText, expectedText, description);
 }
 
 // Export symbols
 window.Sample = Sample;
 window.assert_selection = assertSelection;
 })();