Replace goog.nullFunction with ol.nullFunction

src/ol/renderer/dom/domlayerrenderer.js

@@ -1,5 +1,6 @@
 goog.provide('ol.renderer.dom.Layer');
 
+goog.require('ol');
 goog.require('ol.layer.Layer');
 goog.require('ol.renderer.Layer');
 
@@ -28,14 +29,14 @@ goog.inherits(ol.renderer.dom.Layer, ol.renderer.Layer);
 /**
  * Clear rendered elements.
  */
-ol.renderer.dom.Layer.prototype.clearFrame = goog.nullFunction;
+ol.renderer.dom.Layer.prototype.clearFrame = ol.nullFunction;
 
 
 /**
  * @param {olx.FrameState} frameState Frame state.
  * @param {ol.layer.LayerState} layerState Layer state.
  */
-ol.renderer.dom.Layer.prototype.composeFrame = goog.nullFunction;
+ol.renderer.dom.Layer.prototype.composeFrame = ol.nullFunction;
 
 
 /**

src/ol/renderer/layerrenderer.js

@@ -4,6 +4,7 @@ goog.require('goog.asserts');
 goog.require('goog.events');
 goog.require('goog.events.EventType');
 goog.require('goog.functions');
+goog.require('ol');
 goog.require('ol.ImageState');
 goog.require('ol.Observable');
 goog.require('ol.TileRange');
@@ -47,7 +48,7 @@ goog.inherits(ol.renderer.Layer, ol.Observable);
  * @return {T|undefined} Callback result.
  * @template S,T
  */
-ol.renderer.Layer.prototype.forEachFeatureAtCoordinate = goog.nullFunction;
+ol.renderer.Layer.prototype.forEachFeatureAtCoordinate = ol.nullFunction;
 
 
 /**

src/ol/renderer/maprenderer.js

@@ -335,7 +335,7 @@ ol.renderer.Map.prototype.removeLayerRendererByKey_ = function(layerKey) {
  * Render.
  * @param {?olx.FrameState} frameState Frame state.
  */
-ol.renderer.Map.prototype.renderFrame = goog.nullFunction;
+ol.renderer.Map.prototype.renderFrame = ol.nullFunction;
 
 
 /**