Fix a variety of panel issues

chrome/browser/resources/chromeos/chromevox/cvox2/background/panel.css

 /* 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. */
 
 body {
   border: 0;
   height: 35px;
   margin: 0;
   overflow: hidden;
   padding: 0;
@@ skipping 273 matching lines @@
   right: 15%;
   top: 15%;
 }
 
 #tutorial_main h2 {
   font-family: 'Roboto', sans-serif;
   font-size: 30pt;
   font-weight: bold;
 }
 
+#tutorial_main h2:focus {
+  outline: none
+}
+
 #tutorial_main p,
 #tutorial_main a {
   display: block;
   font-family: 'Roboto', sans-serif;
   font-size: 16pt;
   line-height: 150%;
 }
 
 #tutorial_footer {
   display: flex;
@@ skipping 22 matching lines @@
   border: 1px solid black;
 }
 
 /*
  * The html hidden attribute doesn't make elements not focusable by default.
  * This rule ensures that elements that are hidden truly don't show up.
  */
 *[hidden] {
   display: none !important;
 }