Changes shift key icon & highlight/caps UX.

ui/keyboard/resources/elements/kb-shift-key.html

 <!--
   -- Copyright 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.
   -->
 
 <polymer-element name="kb-shift-key" attributes="lowerCaseKeysetId
-    upperCaseKeysetId" class="shift dark" char="Shift" on-pointerout="{{out}}"
-    extends="kb-key">
+    upperCaseKeysetId" class="shift dark" char="Shift" image="shift.png"
+    on-pointerout="{{out}}" extends="kb-key">
   <template>
     <style>
       .shift-light-wrapper {
         top: 6px;
         height: 10%;
         margin: 0;
         padding: 0;
         position: absolute;
         width: 100%;
       }
 
       .shift-light {
         background-color: #cccccc;
         border: none;
         height: 4px;
         margin: 0 6px 0 auto;
         position: relative;
         width: 4px;
       }
     </style>
     <div class="shift-light-wrapper">
       <div class="shift-light"> </div>
     </div>
     <shadow></shadow>
   </template>
 </polymer-element>