code: function onPopupRedirectAddCustomParam(event) {
    // Form container.
    var html = '<form class="customParamItem form form-bordered no-submit">';
    // OAuth parameter key input.
    html += '<input type="text" class="form-control customParamKey" ' +
        'placeholder="OAuth Parameter Key"/>';
    // OAuth parameter value input.
    html += '<input type="text" class="form-control customParamValue" ' +
        'placeholder="OAuth Parameter Value"/>';
    // Button to remove current key/value pair.
    html += '<button class="btn btn-block btn-primary">Remove</button>';
    html += '</form>';
    // Create jQuery node.
    var $node = $(html);
    // Add button click event listener to remove item.
    $node.find('button').on('click', function(e) {
      // Remove button click event listener.
      $(this).off('click');
      // Get row container and remove it.
      $(this).closest('form.customParamItem').remove();
      e.preventDefault();
    });
    // Append constructed row to parameter list container.
    $("#popup-redirect-custom-parameters").append($node);
  }
docs: Adds a new row to insert an OAuth custom parameter key/value pair.
  @param {!jQuery.Event} event The jQuery event object.