the use of worker does not depend on the map (#1814)

* the use of worker does not depend on the map

* update

Author: deyihu

src/core/worker/WorkerPool.js

@@ -1,3 +1,4 @@
+import { requestAnimFrame } from '../util';
 import { getWorkerSourcePath } from './Worker';
 
 const hardwareConcurrency = typeof window !== 'undefined' ? (window.navigator.hardwareConcurrency || 4) : 0;
@@ -98,10 +99,17 @@ export default class WorkerPool {
 }
 
 let globalWorkerPool;
-
 export function getGlobalWorkerPool() {
     if (!globalWorkerPool) {
         globalWorkerPool = new WorkerPool();
     }
     return globalWorkerPool;
 }
+
+function frameLoop() {
+    getGlobalWorkerPool().commit();
+    requestAnimFrame(frameLoop);
+}
+if (requestAnimFrame) {
+    requestAnimFrame(frameLoop);
+}

src/renderer/map/MapCanvasRenderer.js

@@ -5,7 +5,6 @@ import Point from '../../geo/Point';
 import Canvas2D from '../../core/Canvas';
 import MapRenderer from './MapRenderer';
 import Map from '../../map/Map';
-import { getGlobalWorkerPool } from '../../core/worker/WorkerPool';
 
 /**
  * @classdesc
@@ -612,7 +611,6 @@ class MapCanvasRenderer extends MapRenderer {
         this._frameTimestamp = framestamp;
         this._resizeCount = 0;
         this.renderFrame(framestamp);
-        getGlobalWorkerPool().commit();
         // Keep registering ourselves for the next animation frame
         this._animationFrame = requestAnimFrame((framestamp) => { this._frameLoop(framestamp); });
     }