Move the static worker pool instance to style.js

This is still not great, but it's better than having it in Dispatcher.
Ultimately the right place to put it is at the root level, i.e.
mapbox-gl.js, and then pass it through, but that will be a noisy change
due the number of 'new Map()' and 'new Style()' in the unit tests

js/style/style.js

@@ -18,12 +18,15 @@ var QueryFeatures = require('../source/query_features');
 var SourceCache = require('../source/source_cache');
 var styleSpec = require('./style_spec');
 var StyleFunction = require('./style_function');
+var WorkerPool = require('../util/worker_pool');
+
+var workerPool = new WorkerPool();
 
 module.exports = Style;
 
 function Style(stylesheet, animationLoop, workerCount) {
     this.animationLoop = animationLoop || new AnimationLoop();
-    this.dispatcher = new Dispatcher(workerCount || 1, this);
+    this.dispatcher = new Dispatcher(workerPool, workerCount || 1, this);
     this.spriteAtlas = new SpriteAtlas(1024, 1024);
     this.lineAtlas = new LineAtlas(256, 512);
 

js/util/dispatcher.js

@@ -1,11 +1,9 @@
 'use strict';
 
-var WorkerPool = require('./worker_pool');
 var util = require('./util');
 var Actor = require('./actor');
 
 module.exports = Dispatcher;
-Dispatcher.workerPool = new WorkerPool();
 
 /**
  * Responsible for sending messages from a {@link Source} to an associated
@@ -14,11 +12,12 @@ Dispatcher.workerPool = new WorkerPool();
  * @interface Dispatcher
  * @private
  */
-function Dispatcher(length, parent) {
+function Dispatcher(workerPool, length, parent) {
+    this.workerPool = workerPool;
     this.actors = [];
     this.currentActor = 0;
     this.id = util.uniqueId();
-    var workers = Dispatcher.workerPool.acquire(this.id, length);
+    var workers = this.workerPool.acquire(this.id, length);
     for (var i = 0; i < workers.length; i++) {
         var worker = workers[i];
         var actor = new Actor(worker, parent, this.id);
@@ -68,7 +67,7 @@ Dispatcher.prototype = {
     },
 
     remove: function() {
-        Dispatcher.workerPool.release(this.id);
+        this.workerPool.release(this.id);
         this.actors = [];
     }
 };

test/js/util/dispatcher.test.js

@@ -4,15 +4,15 @@ var test = require('tap').test;
 var proxyquire = require('proxyquire');
 var Dispatcher = require('../../../js/util/dispatcher');
 var WebWorker = require('../../../js/util/web_worker');
-var originalWorkerPool = Dispatcher.workerPool;
+var WorkerPool = require('../../../js/util/worker_pool');
 
 test('Dispatcher', function (t) {
     t.test('requests and releases workers from pool', function (t) {
         var dispatcher;
         var workers = [new WebWorker(), new WebWorker()];
 
         var releaseCalled = [];
-        Dispatcher.workerPool = {
+        var workerPool = {
             acquire: function (id, count) {
                 t.equal(count, 2);
                 return workers;
@@ -22,13 +22,12 @@ test('Dispatcher', function (t) {
             }
         };
 
-        dispatcher = new Dispatcher(2, {});
+        dispatcher = new Dispatcher(workerPool, 2, {});
         t.same(dispatcher.actors.map(function (actor) { return actor.target; }), workers);
         dispatcher.remove();
         t.equal(dispatcher.actors.length, 0, 'actors discarded');
         t.same(releaseCalled, [dispatcher.id]);
 
-        restoreWorkerPool();
         t.end();
     });
 
@@ -38,7 +37,8 @@ test('Dispatcher', function (t) {
         var ids = [];
         function Actor (target, parent, mapId) { ids.push(mapId); }
 
-        var dispatchers = [new Dispatcher(1, {}), new Dispatcher(1, {})];
+        var workerPool = new WorkerPool();
+        var dispatchers = [new Dispatcher(workerPool, 1, {}), new Dispatcher(workerPool, 1, {})];
         t.same(ids, dispatchers.map(function (d) { return d.id; }));
 
         t.end();
@@ -47,12 +47,3 @@ test('Dispatcher', function (t) {
     t.end();
 });
 
-test('after', function (t) {
-    restoreWorkerPool();
-    t.end();
-});
-
-function restoreWorkerPool () {
-    Dispatcher.workerPool = originalWorkerPool;
-}
-