Remove goog.isNull in renderer classes

src/ol/renderer/dom/domimagelayerrenderer.js

@@ -103,14 +103,14 @@ ol.renderer.dom.ImageLayer.prototype.prepareFrame =
       !ol.extent.isEmpty(renderedExtent)) {
     var projection = viewState.projection;
     var sourceProjection = imageSource.getProjection();
-    if (!goog.isNull(sourceProjection)) {
+    if (sourceProjection) {
       goog.asserts.assert(ol.proj.equivalent(projection, sourceProjection),
           'projection and sourceProjection are equivalent');
       projection = sourceProjection;
     }
     var image_ = imageSource.getImage(renderedExtent, viewResolution,
         frameState.pixelRatio, projection);
-    if (!goog.isNull(image_)) {
+    if (image_) {
       var loaded = this.loadImage(image_);
       if (loaded) {
         image = image_;
@@ -118,7 +118,7 @@ ol.renderer.dom.ImageLayer.prototype.prepareFrame =
     }
   }
 
-  if (!goog.isNull(image)) {
+  if (image) {
     var imageExtent = image.getExtent();
     var imageResolution = image.getResolution();
     var transform = goog.vec.Mat4.createNumber();

src/ol/renderer/dom/dommaprenderer.js

@@ -159,7 +159,7 @@ ol.renderer.dom.Map.prototype.getType = function() {
  */
 ol.renderer.dom.Map.prototype.renderFrame = function(frameState) {
 
-  if (goog.isNull(frameState)) {
+  if (!frameState) {
     if (this.renderedVisible_) {
       goog.style.setElementShown(this.layersPane_, false);
       this.renderedVisible_ = false;

src/ol/renderer/dom/domtilelayerrenderer.js

@@ -148,7 +148,7 @@ ol.renderer.dom.TileLayer.prototype.prepareFrame =
       if (!fullyLoaded) {
         childTileRange = tileGrid.getTileCoordChildTileRange(
             tile.tileCoord, tmpTileRange, tmpExtent);
-        if (!goog.isNull(childTileRange)) {
+        if (childTileRange) {
           findLoadedTiles(z + 1, childTileRange);
         }
       }
@@ -376,7 +376,7 @@ ol.renderer.dom.TileLayerZ_.prototype.addTile = function(tile, tileGutter) {
       ((tileCoordX - this.tileCoordOrigin_[1]) * tileSize[0]) + 'px';
   tileElementStyle.top =
       ((this.tileCoordOrigin_[2] - tileCoordY) * tileSize[1]) + 'px';
-  if (goog.isNull(this.documentFragment_)) {
+  if (!this.documentFragment_) {
     this.documentFragment_ = document.createDocumentFragment();
   }
   goog.dom.appendChild(this.documentFragment_, tileElement);
@@ -388,7 +388,7 @@ ol.renderer.dom.TileLayerZ_.prototype.addTile = function(tile, tileGutter) {
  * FIXME empty description for jsdoc
  */
 ol.renderer.dom.TileLayerZ_.prototype.finalizeAddTiles = function() {
-  if (!goog.isNull(this.documentFragment_)) {
+  if (this.documentFragment_) {
     goog.dom.appendChild(this.target, this.documentFragment_);
     this.documentFragment_ = null;
   }

src/ol/renderer/dom/domvectorlayerrenderer.js

@@ -138,7 +138,7 @@ ol.renderer.dom.VectorLayer.prototype.composeFrame =
 
   var replayGroup = this.replayGroup_;
 
-  if (!goog.isNull(replayGroup) && !replayGroup.isEmpty()) {
+  if (replayGroup && !replayGroup.isEmpty()) {
 
     context.globalAlpha = layerState.opacity;
     replayGroup.replay(context, pixelRatio, transform, viewRotation,
@@ -178,7 +178,7 @@ ol.renderer.dom.VectorLayer.prototype.dispatchEvent_ =
  */
 ol.renderer.dom.VectorLayer.prototype.forEachFeatureAtCoordinate =
     function(coordinate, frameState, callback, thisArg) {
-  if (goog.isNull(this.replayGroup_)) {
+  if (!this.replayGroup_) {
     return undefined;
   } else {
     var resolution = frameState.viewState.resolution;
@@ -298,7 +298,7 @@ ol.renderer.dom.VectorLayer.prototype.prepareFrame =
       this.dirty_ = this.dirty_ || dirty;
     }
   };
-  if (!goog.isNull(vectorLayerRenderOrder)) {
+  if (vectorLayerRenderOrder) {
     /** @type {Array.<ol.Feature>} */
     var features = [];
     vectorSource.forEachFeatureInExtentAtResolution(extent, resolution,