ChromeOS OOBE: display icons specific to screen DPI.

chrome/browser/resources/chromeos/login/oobe_buttons.html

 <!-- 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. -->
 
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-iconset-svg/iron-iconset-svg.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-fab/paper-fab.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 
@@ skipping 80 matching lines @@
 
 <!--
   Material design button that shows an icon and displays text.
 
   Example:
     <oobe-welcome-secondary-button icon="close">
       <div i18n-content="oobeCloseButtonText"></div>
     </oobe-welcome-secondary-button>
 
   Attributes:
-    'icon' - a name of icon from material design set to show on button.
+    1x and 2x icons:
+      'icon1x' - a name of icon from material design set to show on button.
+      'icon2x' - a name of icon from material design set to show on button.
     'label-for-aria' - accessibility label.
 -->
 <dom-module id="oobe-welcome-secondary-button">
   <link rel="stylesheet" href="oobe_welcome_secondary_button.css">
   <template>
     <paper-button id="button" aria-label$="[[labelForAria]]">
       <div id="container" class="flex layout vertical center self-stretch">
         <div id="subcontainer"
             class="flex layout horizontal center self-stretch">
-          <iron-icon icon="[[icon]]" class="oobe-icon"></iron-icon>
+          <hd-iron-icon icon1x="[[icon1x]]" icon2x="[[icon2x]]"
+              class="oobe-icon">
+          </hd-iron-icon>
           <content></content>
         </div>
       </div>
     </paper-button>
   </template>
 </dom-module>