Webgl / remove handling of element_index_uint extension

From now on we will assume this extension is always enabled.

An error message have been added in the unlikely scenario of a lack
of support.

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

@@ -89,7 +89,7 @@ describe('ol.renderer.webgl.Layer', function() {
 
     beforeEach(function() {
       vertexBuffer = new Float32Array(100);
-      indexBuffer = new Uint16Array(100);
+      indexBuffer = new Uint32Array(100);
       instructions = new Float32Array(100);
       elementIndex = 3;
 

test/spec/ol/webgl/buffer.test.js

@@ -2,7 +2,6 @@ import WebGLArrayBuffer, {getArrayClassForType} from '../../../../src/ol/webgl/B
 import {
   ARRAY_BUFFER,
   ELEMENT_ARRAY_BUFFER,
-  EXTENSIONS as WEBGL_EXTENSIONS,
   STATIC_DRAW,
   STREAM_DRAW
 } from '../../../../src/ol/webgl.js';
@@ -37,11 +36,6 @@ describe('ol.webgl.Buffer', function() {
       expect(getArrayClassForType(ARRAY_BUFFER)).to.be(Float32Array);
       expect(getArrayClassForType(ELEMENT_ARRAY_BUFFER)).to.be(Uint32Array);
     });
-
-    it('returns the correct typed array constructor (without OES uint extension)', function() {
-      WEBGL_EXTENSIONS.length = 0;
-      expect(getArrayClassForType(ELEMENT_ARRAY_BUFFER)).to.be(Uint16Array);
-    });
   });
 
   describe('populate methods', function() {

test/spec/ol/worker/webgl.test.js

@@ -45,25 +45,6 @@ describe('ol/worker/webgl', function() {
 
         worker.postMessage(message);
       });
-
-      it('responds with buffer data (fallback to Uint16Array)', function(done) {
-        worker.addEventListener('error', done);
-
-        worker.addEventListener('message', function(event) {
-          expect(event.data.indexBuffer).to.eql(Uint16Array.BYTES_PER_ELEMENT * 6);
-          done();
-        });
-
-        const instructions = new Float32Array(POINT_INSTRUCTIONS_COUNT);
-
-        const message = {
-          type: WebGLWorkerMessageType.GENERATE_BUFFERS,
-          renderInstructions: instructions,
-          useShortIndices: true
-        };
-
-        worker.postMessage(message);
-      });
     });
   });