ChromeOS OOBE: display icons specific to screen DPI.

chrome/browser/resources/chromeos/login/oobe_buttons.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.
 
 Polymer({
   is: 'oobe-text-button',
 
   properties: {
     disabled: {type: Boolean, value: false, reflectToAttribute: true},
 
@@ skipping 53 matching lines @@
   onClick_: function(e) {
     if (this.disabled)
       e.stopPropagation();
   }
 });
 
 Polymer({
   is: 'oobe-welcome-secondary-button',
 
   properties: {
-    icon: String,
+    icon1x: String,
+    icon2x: String,
 
     /* Note that we are not using "aria-label" property here, because
      * we want to pass the label value but not actually declare it as an
      * ARIA property anywhere but the actual target element.
      */
     labelForAria: String
   },
 
   focus: function() {
     this.$.button.focus();
   },
 });