Switch dashboard to new flexbox.

dashboard/dashboard/static/base.css

 /**
  * Copyright 2015 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.
  */
 
 html {
   height: 100%;
 }
 
 body {
   line-height: 1.4;
   font: normal 13px arial,sans-serif;
   color: #222;
   background-color: #fff;
   margin: 0;
   padding: 0 10px;
   display: flex;
-  display: -webkit-flex;
   flex-direction: column;
-  -webkit-flex-direction: column;
   min-height: 100%;
 }
 
 nav-bar {
   width: 100%;
 }
 
 h1 {
   align-self: center;
-  -webkit-align-self: center;
 }
 
 a:link {
   color: #15c;
 }
 
 a:visited {
   color: #61c;
 }
 
@@ skipping 33 matching lines @@
 
 /* Buttons */
 .kennedy-button, .kennedy-button-submit {
   border-radius: 2px;
   font-size: 11px;
   font-weight: bold;
   min-width: 54px;
   height: 27px;
   line-height: 27px;
   padding: 0px 8px;
-  -webkit-user-select: none;
+  user-select: none;
 }
 
 .kennedy-button {
   background-color: #f5f5f5;
   border: 1px solid rgba(0,0,0,0.1);
   color: #444;
   background-image: linear-gradient(to bottom, #f5f5f5, #f1f1f1);
   cursor: default;
 }
 
@@ skipping 32 matching lines @@
   position: relative
 }
 
 input[type=checkbox]:checked::after {
   font-size: 1.3em;
   content: "✓";
   position: absolute;
   top: -5px;
   left: -1px;
 }