Adjust the WebUI keyboard css and layout to work better in narrow spaces.

ui/keyboard/resources/elements/kb-row.html

 <!--
   -- Copyright (c) 2013 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.
   -->
 
 <element name="kb-row">
   <template>
     <style>
       @host {
         * {
            -webkit-box-flex: 1;
            display: -webkit-box;
            text-align: center;
            margin-right: 5px;
-           margin-top: 5px;
+           margin-top: 7px;
         }
       }
       content::-webkit-distributed(kb-key) {
         -webkit-flex: 1 auto;
       }
     </style>
     <content select="*"></content>
   </template>
   <script>
     Polymer.register(this);
   </script>
 </element>