Reduce webkit CSS prefixes in ui/ styles

ui/login/account_picker/screen_account_picker.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.
  */
 
 .account-picker.flying-pods #account-picker {
-  -webkit-transition: width 180ms ease,
-                      height 180ms ease;
+  transition: width 180ms ease, height 180ms ease;
 }
 
 #bubble {
   z-index: 1;
 }
 
 #signin-banner-container1 {
   bottom: 100%;
   margin-bottom: 10px;
   position: absolute;
@@ skipping 33 matching lines @@
   display: inline-block;
 }
 
 html[screen=lock] #signin-banner {
   display: inline-block;
   opacity: 0;
   visibility: hidden;
 }
 
 html[screen=lock] #signin-banner.message-set {
-  -webkit-transition: opacity 1s;
   opacity: 1;
+  transition: opacity 1s;
   visibility: visible;
 }