Fix null deref when hiding the PIN keyboard.

ui/login/account_picker/user_pod_row.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.
 
 /**
  * @fileoverview User pod row implementation.
  */
 
 cr.define('login', function() {
   /**
@@ skipping 2556 matching lines @@
       if (app) {
         var activationEvent = cr.doc.createEvent('MouseEvents');
         var ctrlKey = opt_diagnosticMode;
         activationEvent.initMouseEvent('click', true, true, null,
             0, 0, 0, 0, 0, ctrlKey, false, false, false, 0, null);
         app.dispatchEvent(activationEvent);
       }
     },
 
     /**
+     * Toggles pod PIN keyboard visiblity.
+     * @param {!user} username
+     * @param {boolean} visible
+     */
+    setPinVisibility: function(username, visible) {
+      var pod = this.getPodWithUsername_(username);
+      if (!pod) {
+        console.warn('Attempt to change pin visibility to ' + visible +
+            ' for missing pod');
+        return;
+      }
+
+      pod.setPinVisibility(visible);
+    },
+
+    /**
      * Removes user pod from pod row.
-     * @param {string} email User's email.
+     * @param {!user} username
      */
     removeUserPod: function(username) {
       var podToRemove = this.getPodWithUsername_(username);
       if (podToRemove == null) {
-        console.warn('Attempt to remove not existing pod for ' + username +
-            '.');
+        console.warn('Attempt to remove pod that does not exist');
         return;
       }
       this.removeChild(podToRemove);
       if (this.pods.length > 0)
         this.placePods_();
     },
 
     /**
      * Returns index of given pod or -1 if not found.
      * @param {UserPod} pod Pod to look up.
@@ skipping 878 matching lines @@
        if (pod && pod.multiProfilesPolicyApplied) {
          pod.userTypeBubbleElement.classList.remove('bubble-shown');
        }
      }
   };
 
   return {
     PodRow: PodRow
   };
 });