ChromeOS OOBE: Fix OK button on Welcome screen.

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 24 matching lines @@
     </oobe-icon-button>
 
   Attributes:
     'disabled' - button is disabled when the attribute is set.
     'inverse' - makes text white and background blue
     'label-for-aria' - accessibility label.
 -->
 <dom-module id="oobe-text-button">
   <link rel="stylesheet" href="oobe_text_button.css">
   <template>
+    <style>
+      :root {
+        --paper-button-flat-keyboard-focus: {
+          border-color: var(--oobe-text-button-focused-border-color);
+          border-radius: 2px;
+          border-style: solid;
+          border-width: 2px;
+        };
+      }
+    </style>
     <paper-button id="textButton" on-tap="onClick_" disabled="[[disabled]]"
         inverse$="[[inverse]]" aria-label$="[[labelForAria]]">
       <div id="container"
           class="flex layout horizontal center center-justified self-stretch">
         <content></content>
       </div>
     </paper-button>
   </template>
 </dom-module>
 
@@ skipping 57 matching lines @@
             class="flex layout horizontal center self-stretch">
           <hd-iron-icon icon1x="[[icon1x]]" icon2x="[[icon2x]]"
               class="oobe-icon">
           </hd-iron-icon>
           <content></content>
         </div>
       </div>
     </paper-button>
   </template>
 </dom-module>