Compile ui/keyboard/ JS, part 1: remove all warnings

ui/keyboard/resources/elements/kb-altkey-data.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.
 
 (function() {
   var altKeys = {};
   var idMap = {};
 
     /**
      * Creates a unique identifier based on the key provided.
@@ skipping 13 matching lines @@
     }
 
     Polymer('kb-altkey-data', {
 
       /**
        * Retrieves a list of alternative keys to display on a long-press.
        * @param {string} char The base character.
        * @param {boolean=} opt_force If true, force the creation of a list
        *    even if empty. Used when constructing a set of alternates for keys
        *    with hintTexts.
-       * @return {?Object.{id: string, list: string}}
+       * @return {?{id: string, list: string}}
        */
        getAltkeys: function(char, opt_force) {
         var id = idMap[char];
         if (id) {
           return {
             'id': id,
             'keys': altKeys[id]
           };
         }
         if (opt_force) {
@@ skipping 72 matching lines @@
               prepend = true;
           }
           set.id = altKeys.id;
           set.offset = leftOffset;
           return set;
         }
       },
 
     });
 })();