Add <a is="action-link">, a web component extension of <a> for in-page actions.

chrome/browser/resources/user_manager/user_manager_tutorial.css

 /* Copyright 2014 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.
  */
 
 .tutorial-slide {
   -webkit-transition: opacity 200ms ease-in-out;
   background-color: white;
   border-radius: 2px;
   bottom: 0;
@@ skipping 74 matching lines @@
   line-height: 20px;
 }
 
 .slide-buttons {
   bottom: 20px;
   position: absolute;
   text-align: center;
   width: 100%;
 }
 
-.slide-buttons .link-button {
+.slide-buttons [is='action-link'] {
   width: 100%;
 }
 
 .slide-buttons button {
   bottom: 0;
   height: 35px;
   padding: 0 15px;
   width: 138px;
 }
 
@@ skipping 71 matching lines @@
   height: 16px;
   position: absolute;
   right: 5px;
   top: 5px;
   width: 16px;
 }
 
 html[dir=rtl] #slide-not-you #dismiss-bubble-button {
   left: 5px;
 }