Move forEachReadyVisibleLayer into WebGL renderer

src/ol/renderer/webgl/webglmaprenderer.js

@@ -302,6 +302,26 @@ ol.renderer.webgl.Map.prototype.disposeInternal = function() {
 };
 
 
+/**
+ * @param {function(this: T, ol.layer.Layer, ol.renderer.webgl.Layer, number)} f
+ *     Function.
+ * @param {T=} opt_obj Object.
+ * @template T
+ */
+ol.renderer.webgl.Map.prototype.forEachReadyVisibleLayer =
+    function(f, opt_obj) {
+  var layers = this.map.getLayers();
+  if (goog.isDef(layers)) {
+    layers.forEach(function(layer, index) {
+      if (layer.isReady() && layer.getVisible()) {
+        var layerRenderer = this.getLayerRenderer(layer);
+        f.call(opt_obj, layer, layerRenderer, index);
+      }
+    }, this);
+  }
+};
+
+
 /**
  * @return {WebGLRenderingContext} GL.
  */