Added JSDoc to a function missing comment.

Review URL: http://codereview.chromium.org/7799022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98822 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/chromeos/login/oobe_screen_update.js

@@ -47,6 +47,10 @@ cr.define('oobe', function() {
     }
   };
 
+  /**
+   * Registers Escape accelerator to cancel update and
+   * makes 'press Escape to cancel update' hint visible.
+   */
   UpdateScreen.enableUpdateCancel = function() {
     $('update-cancel-hint').hidden = false;
     document.addEventListener('keydown', function(e) {