Update Virtual Keybaord icons.

ui/keyboard/resources/elements/kb-key.js

 // Copyright 2014 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('kb-key', {
   /**
    * The background image to display on this key. Does not display an
    * image if this is the empty string.
    * @type {string}
    */
@@ skipping 49 matching lines @@
 
   /**
    * Called when the image attribute changes. This is used to set the
    * background image of the key.
    * TODO(rsadam): Remove when polymer {{}} syntax regression is fixed.
    */
   imageChanged: function() {
     if (!this.image) {
       this.$.key.style.backgroundImage = "none";
     } else {
+      // If no extension provided, default to svg.
+      var image =
+          this.image.split('.').length > 1 ? this.image : this.image + ".svg";
       this.$.key.style.backgroundImage =
-          "url(images/" + this.image + ".svg)";
+          "url(images/" + image + ")";
     }
   },
 
   /**
    * Returns a subset of the key attributes.
    * @param {string} caller The id of the function that called
    *     populateDetails.
    * @return {Object} Mapping of attributes for the key element.
    */
   populateDetails: function(caller) {
@@ skipping 20 matching lines @@
     return detail;
   }
 });
 ;
 
 Polymer('kb-hide-keyboard-key', {
   up: function(event) {
     hideKeyboard();
   },
 });