Allow plugins to specify a module, and check for module_exists().

lib/Drupal/views/Plugin/Discovery/ViewsDiscovery.php

@@ -29,7 +29,9 @@ public function getDefinitions() {
         $theme_file = "$module.views.inc";
       }
 
-      $definition['module'] = $module_dir;
+      if (!isset($definition['module'])) {
+        $definition['module'] = $module_dir;
+      }
       if (!isset($definition['theme path'])) {
         $definition['theme path'] = $theme_path;
       }

views.module

@@ -1336,6 +1336,11 @@ function views_fetch_plugin_names($type, $key = NULL, $base = array()) {
     if ($key && (empty($plugin['type']) || $plugin['type'] != $key)) {
       continue;
     }
+    // @todo While Views is providing on behalf of core modules, check to see
+    //   if they are enabled or not.
+    if (isset($plugin['module']) && !module_exists($plugin['module'])) {
+      continue;
+    }
 
     if (empty($plugin['no ui']) && (empty($base) || empty($plugin['base']) || array_intersect($base, $plugin['base']))) {
       $plugins[$id] = $plugin['title'];