Remove remaining use of inherits in src

src/ol/source/Raster.js

@@ -72,21 +72,21 @@ const RasterOperationType = {
 };
 
 
-/**
- * @classdesc
- * Events emitted by {@link module:ol/source/Raster} instances are instances of this
- * type.
- *
- * @constructor
- * @extends {module:ol/events/Event}
- * @param {string} type Type.
- * @param {module:ol/PluggableMap~FrameState} frameState The frame state.
- * @param {Object} data An object made available to operations.
- */
-class RasterSourceEvent {
+class RasterSourceEvent extends Event {
 
+  /**
+   * @classdesc
+   * Events emitted by {@link module:ol/source/Raster} instances are instances of this
+   * type.
+   *
+   * @constructor
+   * @extends {module:ol/events/Event}
+   * @param {string} type Type.
+   * @param {module:ol/PluggableMap~FrameState} frameState The frame state.
+   * @param {Object} data An object made available to operations.
+   */
   constructor(type, frameState, data) {
-    Event.call(this, type);
+    super(type);
 
     /**
      * The raster extent.
@@ -114,8 +114,6 @@ class RasterSourceEvent {
 
 }
 
-inherits(RasterSourceEvent, Event);
-
 /**
  * @typedef {Object} Options
  * @property {Array.<module:ol/source/Source|module:ol/layer/Layer>} sources Input
@@ -137,19 +135,19 @@ inherits(RasterSourceEvent, Event);
  */
 
 
-/**
- * @classdesc
- * A source that transforms data from any number of input sources using an
- * {@link module:ol/source/Raster~Operation} function to transform input pixel values into
- * output pixel values.
- *
- * @constructor
- * @extends {module:ol/source/Image}
- * @fires ol/source/Raster~RasterSourceEvent
- * @param {module:ol/source/Raster~Options=} options Options.
- * @api
- */
-class RasterSource {
+class RasterSource extends ImageSource {
+  /**
+   * @classdesc
+   * A source that transforms data from any number of input sources using an
+   * {@link module:ol/source/Raster~Operation} function to transform input pixel values into
+   * output pixel values.
+   *
+   * @constructor
+   * @extends {module:ol/source/Image}
+   * @fires ol/source/Raster~RasterSourceEvent
+   * @param {module:ol/source/Raster~Options=} options Options.
+   * @api
+   */
   constructor(options) {
 
     /**
@@ -245,7 +243,7 @@ class RasterSource {
       wantedTiles: {}
     };
 
-    ImageSource.call(this, {});
+    super({});
 
     if (options.operation !== undefined) {
       this.setOperation(options.operation, options.lib);
@@ -421,8 +419,6 @@ class RasterSource {
   }
 }
 
-inherits(RasterSource, ImageSource);
-
 
 /**
  * A reusable canvas context.