Remove dead code for system VK.

ui/keyboard/resources/elements/kb-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-key" extends="kb-key-base" attributes="image keyCode
-    keyName shiftModifier sound stretch weight">
-  <template>
-    <style>
-      :host {
-        background-color: #ffffff;
-        border-radius: 1px;
-        border-style: solid;
-        border-width: 0px 0px;
-        color: #666666;
-        font-family: roboto-bold;
-        font-weight: 100;
-      }
-
-      :host .key {
-        background-image: none;
-        background-position: center;
-        background-repeat: no-repeat;
-        background-size: contain;
-        bottom: 0;
-        height: 1.2em;
-        left: 0;
-        margin: auto;
-        position: absolute;
-        right: 0;
-        text-align: center;
-        top: 0;
-      }
-
-      :host([align=left]) .key {
-        padding-left: 1em;
-      }
-
-      /* TODO(rsadam@): Remove when we fully switch to native shadow dom. */
-      /* TODO(rsadam@): Move shift key rules to kb-shift-key. */
-      kb-shift-key .key,
-      :host(kb-shift-key) .key {
-        height: 70%;
-        width: auto;
-      }
-
-      :host([image].cursor) .key {
-        height: 85%;
-      }
-
-      :host([image]) .key {
-        height: 30%;
-      }
-
-      :host([image].tab) .key {
-        height: 40%;
-      }
-
-      :host .hint,
-      :host([invert]) key {
-        color: #bababa;
-      }
-
-      :host .hint {
-        font-size: 70%;
-        position: absolute;
-        right: 7%;
-        top: 5%;
-      }
-
-      :host-context(.hide-hint-text) .hint {
-        display: none;
-      }
-
-      :host([invert]) .hint {
-        color: #666666;
-      }
-
-      :host(.dark) {
-        font-size: 70%;
-      }
-
-      :host(.dark.active) {
-        background-color: #cccccc;
-      }
-
-      :host(.active) {
-        background-color: #dddddd;
-        background-size: cover;
-      }
-
-      :host(.dark:not(.active)) {
-        background-color: #555555;
-      }
-
-      :host(:not(.dark):not(.active)) {
-        background-color: #ffffff;
-        background-size: cover;
-      }
-    </style>
-    <div id="key" class="key">
-      <content></content>
-    </div>
-    <div class="hint" part="hint">{{hintText}}</div>
-  </template>
-</polymer-element>
-
-<!-- Special keys -->
-<polymer-element name="kb-abc-key" class="symbol dark" char="Invalid"
-    extends="kb-key" weight="125">
-</polymer-element>
-
-<polymer-element name="kb-hide-keyboard-key" class="hide-keyboard dark"
-    align="center" attributes="showMenu" char="Invalid" extends="kb-key">
-</polymer-element>