Fix the hover/focus CSS for the buttons in the desktop User Manager.

chrome/browser/resources/user_manager/control_bar.css

 /* Copyright 2013 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.
  */
 
 /* Overrides of styles in chrome/browser/resources/chromeos/login/header_bar.js
 * that are needed by the desktop user chooser screen
 */
 #login-header-bar {
   -webkit-padding-after: 16px;
@@ skipping 44 matching lines @@
 
 #login-header-bar button {
   -webkit-padding-start: 24px;
   background-color: white;
   background-position: left center;
   background-repeat: no-repeat;
   border: none;
   box-shadow: none;
   cursor: pointer;
   font-size: 12px;
+  opacity: 0.8;
+}
+
+#login-header-bar button:active,
+#login-header-bar button:focus,
+#login-header-bar button:hover {
+  opacity: 1;
+}
+
+#login-header-bar button:focus {
+  text-decoration: underline;
 }
 
 #logo {
   content: -webkit-image-set(
       url('../../../app/theme/%DISTRIBUTION%/product_logo_name_48.png') 1x,
       url('../../../app/theme/%DISTRIBUTION%/product_logo_name_96.png') 2x);
   height: 18px;
   position: absolute;
   right: 16px;
   top: 20px;
 }
 
 html[dir=rtl] #logo {
   left: 16px;
 }