Replace usages of old createElement string second argument API

This usage can break when Custom Elements v0 is turned off, so this
CL updates to a ElementCreationOptions object.

Existing tests should catch issues with this change.

Change-Id: Ifb410725c9a1972202b60261b96941503cb79636
Cq-Do-Not-Cancel-Tryjobs: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2519386
Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825621}

chrome/browser/resources/accessibility/accessibility.js

@@ -350,7 +350,8 @@ function getNameForAccessibilityMode(mode) {
 
 function createModeElement(mode, data, globalStateName) {
   const currentMode = data['a11yMode'];
-  const link = document.createElement('a', 'action-link');
+  const link = document.createElement('a', {is: 'action-link'});
+  link.setAttribute('is', 'action-link');
   link.setAttribute('role', 'button');
 
   const stateText = ((currentMode & mode) != 0) ? 'true' : 'false';