Make layers responsible for creating layer renderers

src/ol/layer/base.js

@@ -54,6 +54,15 @@ ol.layer.Base = function(options) {
 ol.inherits(ol.layer.Base, ol.Object);
 
 
+/**
+ * Create a renderer for this layer.
+ * @abstract
+ * @param {ol.renderer.Map} mapRenderer The map renderer.
+ * @return {ol.renderer.Layer} A layer renderer.
+ */
+ol.layer.Base.prototype.createRenderer = function(mapRenderer) {};
+
+
 /**
  * @return {ol.LayerState} Layer state.
  */