code: function withCommand(element, action) {
    var command = element.getAttribute('data-command');
    if (!command) {
      command = element.querySelector('*[data-command]')
              .getAttribute('data-command');
    }
  
    if (command) {
      action(command);
    }
    else {
      console.warn('Missing data-command for ' + util.findCssSelector(element));
    }
  }
docs: Helper to find the 'data-command' attribute and call some action on it.
  @see |updateCommand()| and |executeCommand()|