Gamelab: enable custom marshaling of SpriteSheet

apps/src/gamelab/GameLabP5.js

@@ -464,6 +464,7 @@ GameLabP5.prototype.getCustomMarshalObjectList = function () {
     { instance: window.p5 },
     { instance: this.p5.Camera },
     { instance: this.p5.Animation },
+    { instance: this.p5.SpriteSheet },
     { instance: window.p5.Vector },
     { instance: window.p5.Color },
     { instance: window.p5.Image },

apps/test/integration/levelSolutions/gamelab/custom_marshal.js

@@ -0,0 +1,31 @@
+import {gamelabLevelDefinition} from '../../gamelabLevelDefinition';
+import {testAsyncProgramGameLab} from '../../util/levelTestHelpers';
+
+// These tests force us to custom marshal p5 objects properly, and are
+// written to fail if they are improperly marshaled.
+module.exports = {
+  app: "gamelab",
+  skinId: "gamelab",
+  levelDefinition: gamelabLevelDefinition,
+  tests: [
+    testAsyncProgramGameLab(
+      'Game Lab custom marshal SpriteSheet returned from loadSpriteSheet()',
+      `
+        // create empty SpriteSheet with no images or frames
+        var spriteSheet = loadSpriteSheet();
+        // loadAnimation() will error out if we try to pass in an improperly
+        // marshaled SpriteSheet object.
+        var animation = loadAnimation(spriteSheet);
+        console.log('done');
+      `,
+      function isProgramDone() {
+        const debugOutput = document.getElementById('debug-output').textContent;
+        return debugOutput.includes('done');
+      },
+      function validateResult(assert) {
+        const debugOutput = document.getElementById('debug-output').textContent;
+        assert.notInclude(debugOutput, 'function');
+      }
+    ),
+  ]
+};