Update color/thickness of ChromeOS login shelf button focus state.

ui/login/oobe.css

 /* Copyright 2014 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.
  *
  * This is the stylesheet used by the Out of the box experience (OOBE) flow,
  * sign in and lock screens.
  */
 
 html,
 body {
@@ skipping 19 matching lines @@
 button {
   font-family: inherit;
   outline: none;
 }
 
 /* Follow same focus coloring as in widgets.css */
 /* Do not apply this style to restricted button state. */
 button.custom-appearance:not(.button-restricted):not(.button-fancy):not(
     [is="gaia-icon-button"]) {
   -webkit-transition: border-color 200ms;
-  border: 1px solid transparent;
+  border: 2px solid transparent;
   /* Don't grey out disabled buttons. */
   color: buttontext !important;
 }
 
 /* ':focus' used three times to increase specificity. */
 button.custom-appearance:focus:focus:focus {
-  border-color: rgb(77, 144, 254);
+  border-color: rgba(66, 133, 244, 0.6); /* #4285f4 */
 }
 
 button:not(.custom-appearance) {
   min-width: 72px !important;
 }
 
 button.button-fancy {
   min-width: 72px !important;
 }
 
@@ skipping 107 matching lines @@
 }
 
 .background-initial {
   opacity: 0;
 }
 
 .throbber {
   -webkit-margin-end: 0.5em;
   margin-top: 1px;
 }