Reduce usage of webkit prefixes in extension examples

chrome/common/extensions/docs/examples/api/browsingData/basic/popup.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.
  */
 
 body {
   margin: 5px 10px 10px;
 }
 
 h1 {
   color: #53637D;
   font: 26px/1.2 Helvetica, sans-serif;
   font-size: 200%;
   margin: 0;
   padding-bottom: 4px;
   text-shadow: white 0 1px 2px;
 }
 
 label {
   color: #222;
   font: 18px/1.4 Helvetica, sans-serif;
   margin: 0.5em 0;
   display: inline-block;
 }
 
 form {
+  transition: transform 0.25s ease;
   width: 563px;
-  -webkit-transition: -webkit-transform 0.25s ease;
 }
 
 button {
   display: block;
   border-radius: 2px;
   box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.1);
   -webkit-user-select: none;
   background: -webkit-linear-gradient(#FAFAFA, #F4F4F4 40%, #E5E5E5);
   border: 1px solid #AAA;
   color: #444;
@@ skipping 11 matching lines @@
   left: 50%;
   top: 50%;
   width: 500px;
   padding: 20px;
   margin: -40px 0 0 -270px;
   opacity: 0;
   background: rgba(0, 0, 0, 0.75);
   border-radius: 5px;
   color: #FFF;
   font: 1.5em/1.2 Helvetica Neue, sans-serif;
-  -webkit-transition: all 1.0s ease;
-  -webkit-transform: scale(0);
+  transition: all 1.0s ease;
+  transform: scale(0);
 }
 
 .overlay a {
   color:  #FFF;
 }
 
 .overlay.visible {
   opacity: 1;
-  -webkit-transform: scale(1);
+  transform: scale(1);
 }