fix: Add polyfill for requestIdleCallback for webkit based browsers

sandbox/src/game.ts

@@ -64,6 +64,7 @@ var game = new ex.Engine({
     filtering: ex.ImageFiltering.Pixel,
     multiSampleAntialiasing: true
   },
+  garbageCollection: true,
   uvPadding: 0,
   physics: {
     colliders: {

src/engine/Polyfill.ts

@@ -52,4 +52,28 @@ export function polyfill() {
   if (typeof window !== 'undefined' && !(<any>window).devicePixelRatio) {
     (<any>window).devicePixelRatio = window.devicePixelRatio || 1;
   }
+
+  /* istanbul ignore next */
+  if (typeof window !== 'undefined' && !(window as any).requestIdleCallback) {
+    // Adapted from https://developer.chrome.com/blog/using-requestidlecallback#checking_for_requestidlecallback
+    (window as any).requestIdleCallback =
+      window.requestIdleCallback ||
+      function (cb: (args: any) => any) {
+        const start = Date.now();
+        return setTimeout(function () {
+          cb({
+            didTimeout: false,
+            timeRemaining: function () {
+              return Math.max(0, 50 - (Date.now() - start));
+            }
+          });
+        }, 1);
+      };
+
+    (window as any).cancelIdleCallback =
+      window.cancelIdleCallback ||
+      function (id: any) {
+        clearTimeout(id);
+      };
+  }
 }