Remove goog.isNull in renderer classes

src/ol/renderer/webgl/webglvectorlayerrenderer.js

@@ -78,7 +78,7 @@ ol.renderer.webgl.VectorLayer.prototype.composeFrame =
   this.layerState_ = layerState;
   var viewState = frameState.viewState;
   var replayGroup = this.replayGroup_;
-  if (!goog.isNull(replayGroup) && !replayGroup.isEmpty()) {
+  if (replayGroup && !replayGroup.isEmpty()) {
     replayGroup.replay(context,
         viewState.center, viewState.resolution, viewState.rotation,
         frameState.size, frameState.pixelRatio, layerState.opacity,
@@ -93,7 +93,7 @@ ol.renderer.webgl.VectorLayer.prototype.composeFrame =
  */
 ol.renderer.webgl.VectorLayer.prototype.disposeInternal = function() {
   var replayGroup = this.replayGroup_;
-  if (!goog.isNull(replayGroup)) {
+  if (replayGroup) {
     var context = this.mapRenderer.getContext();
     replayGroup.getDeleteResourcesFunction(context)();
     this.replayGroup_ = null;
@@ -107,7 +107,7 @@ ol.renderer.webgl.VectorLayer.prototype.disposeInternal = function() {
  */
 ol.renderer.webgl.VectorLayer.prototype.forEachFeatureAtCoordinate =
     function(coordinate, frameState, callback, thisArg) {
-  if (goog.isNull(this.replayGroup_) || goog.isNull(this.layerState_)) {
+  if (!this.replayGroup_ || !this.layerState_) {
     return undefined;
   } else {
     var context = this.mapRenderer.getContext();
@@ -141,7 +141,7 @@ ol.renderer.webgl.VectorLayer.prototype.forEachFeatureAtCoordinate =
  */
 ol.renderer.webgl.VectorLayer.prototype.hasFeatureAtCoordinate =
     function(coordinate, frameState) {
-  if (goog.isNull(this.replayGroup_) || goog.isNull(this.layerState_)) {
+  if (!this.replayGroup_ || !this.layerState_) {
     return false;
   } else {
     var context = this.mapRenderer.getContext();
@@ -233,7 +233,7 @@ ol.renderer.webgl.VectorLayer.prototype.prepareFrame =
     return true;
   }
 
-  if (!goog.isNull(this.replayGroup_)) {
+  if (this.replayGroup_) {
     frameState.postRenderFunctions.push(
         this.replayGroup_.getDeleteResourcesFunction(context));
   }
@@ -266,7 +266,7 @@ ol.renderer.webgl.VectorLayer.prototype.prepareFrame =
       this.dirty_ = this.dirty_ || dirty;
     }
   };
-  if (!goog.isNull(vectorLayerRenderOrder)) {
+  if (vectorLayerRenderOrder) {
     /** @type {Array.<ol.Feature>} */
     var features = [];
     vectorSource.forEachFeatureInExtentAtResolution(extent, resolution,