Polyfill WeakRef (#34025)

Fix #33407

web_src/js/webcomponents/polyfill.test.ts

@@ -0,0 +1,7 @@
+import {weakRefClass} from './polyfills.ts';
+
+test('polyfillWeakRef', () => {
+  const WeakRef = weakRefClass();
+  const r = new WeakRef(123);
+  expect(r.deref()).toEqual(123);
+});