Views Mini Pager Theme does not use route

Problem/Motivation

I ran into this issue will fixing a "bug" on a current project. We have view page, using ajax and a mini-pager. We also have Views Ajax History module turned on. When paging the second time and beyond, you loose the correct url. While investigating this, it seems the mini pager copies a lot from the Full pager, which it should. And the plugin (Drupal\views\Plugin\views\pager\Mini) implements the theme with a variable "#route_name" but never uses it.

So here is a test I did to explain further. There is more to that total issue, but this is the first part for mini-pagers:
Full Pager w/ Views Ajax History:

- Load Page: http://dev-bcd83.pantheonsite.io/ajax-views-full-pager
- Click Page 2, get http://dev-bcd83.pantheonsite.io/ajax-views-full-pager?page=1
- Click Page 3, http://dev-bcd83.pantheonsite.io/ajax-views-full-pager?ajax_page_state[t...

Mini Pager w/ Views Ajax History:

- Load Page, http://dev-bcd83.pantheonsite.io/ajax-views-mini-pager
- Click Next, http://dev-bcd83.pantheonsite.io/ajax-views-mini-pager?page=1
- Click Next, http://dev-bcd83.pantheonsite.io/views/ajax?ajax_page_state[theme]=barti...

Proposed resolution

I believe the views_mini_pager theme needs to add "route_name" as a variable and the preprocess function needs to use the route just like the full pager.

Also, for those that need an immediate fix, this can be accomplished through alters and preprocesses...

function MODULE_theme_registry_alter(&$theme_registry) {
  // Fix core bug with mini pager.
  $theme_registry['views_mini_pager']['variables']['route_name'] = '';
}

// Overwrite preprocess functions.
function MODULE_preprocess_views_mini_pager(&$variables) {
  global $pager_page_array, $pager_total;

  $tags = &$variables['tags'];
  $element = $variables['element'];
  $parameters = $variables['parameters'];
  $route_name = $variables['route_name'];
  $route_parameters = [];

  // Current is the page we are currently paged to.
  $variables['items']['current'] = $pager_page_array[$element] + 1;

  if ($pager_total[$element] > 1 && $pager_page_array[$element] > 0) {
    $options = [
      'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] - 1),
    ];
    $variables['items']['previous']['href'] = \Drupal::url($route_name, $route_parameters, $options);
    if (isset($tags[1])) {
      $variables['items']['previous']['text'] = $tags[1];
    }
    $variables['items']['previous']['attributes'] = new Attribute();
  }

  if ($pager_page_array[$element] < ($pager_total[$element] - 1)) {
    $options = [
      'query' => pager_query_add_page($parameters, $element, $pager_page_array[$element] + 1),
    ];
    $variables['items']['next']['href'] = \Drupal::url($route_name, $route_parameters, $options);
    if (isset($tags[3])) {
      $variables['items']['next']['text'] = $tags[3];
    }
    $variables['items']['next']['attributes'] = new Attribute();
  }
}

Remaining tasks

I've included a patch