Don't create useless temporary variables

src/ol/render/webgl/CircleReplay.js

@@ -196,9 +196,7 @@ WebGLCircleReplay.prototype.getDeleteResourcesFunction = function(context) {
  */
 WebGLCircleReplay.prototype.setUpProgram = function(gl, context, size, pixelRatio) {
   // get the program
-  const fragmentShader = fragment;
+  const program = context.getProgram(fragment, vertex);
-  const vertexShader = vertex;
-  const program = context.getProgram(fragmentShader, vertexShader);
 
   // get the locations
   let locations;

src/ol/render/webgl/LineStringReplay.js

@@ -439,9 +439,7 @@ WebGLLineStringReplay.prototype.getDeleteResourcesFunction = function(context) {
  */
 WebGLLineStringReplay.prototype.setUpProgram = function(gl, context, size, pixelRatio) {
   // get the program
-  const fragmentShader = fragment;
+  const program = context.getProgram(fragment, vertex);
-  const vertexShader = vertex;
-  const program = context.getProgram(fragmentShader, vertexShader);
 
   // get the locations
   let locations;

src/ol/render/webgl/PolygonReplay.js

@@ -873,9 +873,7 @@ WebGLPolygonReplay.prototype.getDeleteResourcesFunction = function(context) {
  */
 WebGLPolygonReplay.prototype.setUpProgram = function(gl, context, size, pixelRatio) {
   // get the program
-  const fragmentShader = fragment;
+  const program = context.getProgram(fragment, vertex);
-  const vertexShader = vertex;
-  const program = context.getProgram(fragmentShader, vertexShader);
 
   // get the locations
   let locations;

src/ol/render/webgl/TextureReplay.js

@@ -271,9 +271,7 @@ WebGLTextureReplay.prototype.createTextures = function(textures, images, texture
  */
 WebGLTextureReplay.prototype.setUpProgram = function(gl, context, size, pixelRatio) {
   // get the program
-  const fragmentShader = fragment;
+  const program = context.getProgram(fragment, vertex);
-  const vertexShader = vertex;
-  const program = context.getProgram(fragmentShader, vertexShader);
 
   // get the locations
   let locations;

src/ol/renderer/webgl/Layer.js

@@ -148,10 +148,7 @@ WebGLLayerRenderer.prototype.composeFrame = function(frameState, layerState, con
 
   const gl = context.getGL();
 
-  const fragmentShader = fragment;
+  const program = context.getProgram(fragment, vertex);
-  const vertexShader = vertex;
-
-  const program = context.getProgram(fragmentShader, vertexShader);
 
   let locations;
   if (!this.defaultLocations_) {