Remove remaining use of inherits in src

src/ol/source/VectorTile.js

@@ -58,24 +58,24 @@ import {createXYZ, extentFromProjection, createForProjection} from '../tilegrid.
  */
 
 
-/**
- * @classdesc
- * Class for layer sources providing vector data divided into a tile grid, to be
- * used with {@link module:ol/layer/VectorTile~VectorTile}. Although this source receives tiles
- * with vector features from the server, it is not meant for feature editing.
- * Features are optimized for rendering, their geometries are clipped at or near
- * tile boundaries and simplified for a view resolution. See
- * {@link module:ol/source/Vector} for vector sources that are suitable for feature
- * editing.
- *
- * @constructor
- * @fires module:ol/source/Tile~TileSourceEvent
- * @extends {module:ol/source/UrlTile}
- * @param {module:ol/source/VectorTile~Options=} options Vector tile options.
- * @api
- */
-class VectorTile {
+class VectorTile extends UrlTile {
 
+  /**
+   * @classdesc
+   * Class for layer sources providing vector data divided into a tile grid, to be
+   * used with {@link module:ol/layer/VectorTile~VectorTile}. Although this source receives tiles
+   * with vector features from the server, it is not meant for feature editing.
+   * Features are optimized for rendering, their geometries are clipped at or near
+   * tile boundaries and simplified for a view resolution. See
+   * {@link module:ol/source/Vector} for vector sources that are suitable for feature
+   * editing.
+   *
+   * @constructor
+   * @fires module:ol/source/Tile~TileSourceEvent
+   * @extends {module:ol/source/UrlTile}
+   * @param {module:ol/source/VectorTile~Options=} options Vector tile options.
+   * @api
+   */
   constructor(options) {
     const projection = options.projection || 'EPSG:3857';
 
@@ -88,7 +88,7 @@ class VectorTile {
       tileSize: options.tileSize || 512
     });
 
-    UrlTile.call(this, {
+    super({
       attributions: options.attributions,
       cacheSize: options.cacheSize !== undefined ? options.cacheSize : 128,
       extent: extent,
@@ -139,8 +139,6 @@ class VectorTile {
 
 }
 
-inherits(VectorTile, UrlTile);
-
 
 /**
  * @return {boolean} The source can have overlapping geometries.