[WebUI] Fix all CSS nits in chrome/browser/resources/chromeos.

chrome/browser/resources/chromeos/login/bubble.css

 /* Copyright (c) 2012 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.
  *
  * Css based bubble.
  */
 
 .bubble {
-  -webkit-box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
   background: white;
   border: 1px solid rgba(0, 0, 0, 0.25);
+  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
   font-size: 12px;
   margin: 2px;
+  max-width: 250px;
   padding: 16px;
   position: absolute;
-  max-width: 250px;
 }
 
 .bubble:before {
-  content: "";
   border-style: solid;
   border-width: 8px;
+  content: '';
   display: block;
   position: absolute;
 }
 
 .bubble-top:before {
   border-color: rgba(0, 0, 0, 0.25) transparent transparent transparent;
   bottom: -16px;
 }
 
 html[dir=ltf] .bubble-top:before {
@@ skipping 25 matching lines @@
 }
 
 html[dir=ltr] .bubble-left:before,
 html[dir=rtl] .bubble-right:before {
   border-color: transparent transparent transparent rgba(0, 0, 0, 0.25);
   right: -16px;
   top: 17px;
 }
 
 .bubble:after {
-  content: "";
   border-style: solid;
   border-width: 8px;
+  content: '';
   display: block;
   position: absolute;
 }
 
 .bubble-top:after {
   border-color: white transparent transparent transparent;
   bottom: -15px;
 }
 
 html[dir=ltr] .bubble-top:after {
@@ skipping 23 matching lines @@
 html[dir=rtl] .bubble-bottom:after {
   right: 17px;
 }
 
 html[dir=ltr] .bubble-left:after,
 html[dir=rtl] .bubble-right:after {
   border-color: transparent transparent transparent white;
   right: -15px;
   top: 17px;
 }