Add unit test for lock and unlock virtual keyboard feature

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 imageSize keyCode keyName shiftModifier weight">
   <template>
     <style>
@@ skipping 172 matching lines @@
   <script>
     Polymer('kb-hide-keyboard-key', {
       /**
        * Timer for a long press event which triggers the display of a keyboard
        * options menu.
        * @type {?Function}
        */
       longPressTimer: undefined,
 
       down: function(event) {
-         var self = this;
-         this.longPressTimer = this.asyncMethod(function() {
-           if (self.longPressTimer) {
-             clearTimeout(self.longPressTimer);
-             self.longPressTimer = undefined;
+         this.longPressTimer = this.async(function() {
+           if (this.longPressTimer) {
+             clearTimeout(this.longPressTimer);
+             this.longPressTimer = undefined;
              var details = {
                left: this.offsetLeft,
                top: this.offsetTop,
                width: this.clientWidth,
              };
              this.fire('show-options', details);
            }
          }, null, LONGPRESS_DELAY_MSEC);
       },
 
       /** @override */
       ready: function() {
         this.super();
         this.image = "keyboard";
       },
 
       up: function(event) {
         if (this.longPressTimer) {
           clearTimeout(this.longPressTimer);
           hideKeyboard();
           this.longPressTimer = undefined;
         }
       }
     });
   </script>
 </polymer-element>