Webgl / add a simple Layer renderer for common logic

This will eventually provides utilities for manipulating & rendering data

test/spec/ol/renderer/webgl/layer.test.js

@@ -0,0 +1,45 @@
+import VectorLayer from '../../../../../src/ol/layer/Vector.js';
+import VectorSource from '../../../../../src/ol/source/Vector.js';
+import WebGLLayerRenderer, {getBlankTexture} from '../../../../../src/ol/renderer/webgl/Layer';
+
+
+describe('ol.renderer.webgl.Layer', function() {
+
+  describe('constructor', function() {
+
+    let target;
+
+    beforeEach(function () {
+      target = document.createElement('div');
+      target.style.width = '256px';
+      target.style.height = '256px';
+      document.body.appendChild(target);
+    });
+
+    afterEach(function () {
+      document.body.removeChild(target);
+    });
+
+    it('creates a new instance', function () {
+      const layer = new VectorLayer({
+        source: new VectorSource()
+      });
+      const renderer = new WebGLLayerRenderer(layer);
+      expect(renderer).to.be.a(WebGLLayerRenderer);
+    });
+
+  });
+
+  describe('getBlankTexture', function() {
+    it('creates a 1x1 white texture', function() {
+      const texture = getBlankTexture();
+      expect(texture.height).to.eql(1);
+      expect(texture.width).to.eql(1);
+      expect(texture.data[0]).to.eql(255);
+      expect(texture.data[1]).to.eql(255);
+      expect(texture.data[2]).to.eql(255);
+      expect(texture.data[3]).to.eql(255);
+    });
+  });
+
+});