[Editing][Codehealth] Rewrite user-select-all-selection.html with 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 499 matching lines @@
    */
   constructor(sampleText) {
     /** @const @type {!HTMLIFame} */
     this.iframe_ = document.createElement('iframe');
     document.body.appendChild(this.iframe_);
     /** @const @type {!HTMLDocument} */
     this.document_ = this.iframe_.contentDocument;
     /** @const @type {!Selection} */
     this.selection_ = this.iframe_.contentWindow.getSelection();
     this.selection_.document = this.document_;
+    this.selection_.document.offsetLeft = this.iframe_.offsetLeft;

[yosin_UTC9, 2016/06/30 03:47:37]

Not sure about these changes.
Document doesn't have |offsetLeft| and |offsetTop| properties.

[yoichio, 2016/07/04 06:28:17]

That's because we need iframe offset to use eventSender.mouseMove.

+    this.selection_.document.offsetTop = this.iframe_.offsetTop;
 
     this.load(sampleText);
   }
 
   /** @return {!HTMLDocument} */
   get document() { return this.document_; }
 
   /** @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) {

[yosin_UTC9, 2016/06/30 03:47:37]

We should have another CL for this change to explicitly state
|assert_selection()| for this case.

       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;
 })();