Changes shift key icon & highlight/caps UX.

ui/keyboard/resources/main.css

 /*
  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.
 */
 
 @font-face {
   font-family: roboto-bold;
   src: url(roboto_bold.ttf);
 }
 
 /**
  * TODO(rsadam@): Remove all these rules once we switch to native
  * shadow dom.
  */
 kb-keyboard.ctrl-active kb-modifier-key[char=Ctrl],
-kb-keyboard.alt-active kb-modifier-key[char=Alt] {
-  background-color: #bbbbbb;
-}
-
-kb-keyboard[keyset="upper"] kb-shift-key.dark /deep/ .key {
-  background-image: url('images/shift-filled.svg');
-}
-
-kb-keyboard[keyset="lower"] kb-shift-key /deep/ .key{
-  background-image: url('images/shift.svg');
+kb-keyboard.alt-active kb-modifier-key[char=Alt],
+kb-keyboard.caps-locked kb-shift-key.dark {
+  -webkit-box-shadow: inset 0 0 3px 2px #aaaaaa;
+  background-color: #cccccc;
 }
 
 /**
 * Controls whether the shift key should be highlighted or not.
 */
-kb-keyboard.caps-locked kb-shift-key.dark /deep/
+kb-keyboard[keyset="upper"] kb-shift-key.dark /deep/
     .shift-light {
     background-color: #4285f4;
 }
 
 .space,
 .dark {
   font-size: 70%;
 }
 
 .dark:not(.active),
 :not(kb-altkey-set) > :not(.dark).active {
   background-color: #dddddd;
 }
 
 .space {
   color: #bbbbbb;
 }