HTML: test WindowProxy self references

html/browsers/the-window-object/self-et-al.window.js

@@ -0,0 +1,43 @@
+function delayed_assert_done(t, w, windowProxySelfReference) {
+  // Let's make sure nobody is being sneaky
+  t.step_timeout(() => {
+    t.step_timeout(() => {
+      assert_equals(w[windowProxySelfReference], w, `${windowProxySelfReference} got cleared after some time`);
+      t.done();
+    }, 0);
+  }, 0);
+}
+
+[
+  "frames",
+  "globalThis",
+  "self",
+  "window"
+].forEach(windowProxySelfReference => {
+  async_test(t => {
+    const frame = document.body.appendChild(document.createElement("iframe")),
+          otherW = frame.contentWindow;
+    assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} is broken`);
+    frame.remove();
+    assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} got cleared after browsing context removal`);
+    assert_true(otherW.closed);
+
+    delayed_assert_done(t, otherW, windowProxySelfReference);
+  }, `iframeWindow.${windowProxySelfReference} before and after removal`);
+
+  async_test(t => {
+    const otherW = window.open();
+    assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} is broken`);
+    otherW.onunload = t.step_func(() => {
+      assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} got cleared after browsing context unload`);
+      t.step_timeout(() => {
+        assert_equals(otherW.opener, null); // Ensure browsing context is discarded
+        assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} got cleared after browsing context removal`);
+        delayed_assert_done(t, otherW, windowProxySelfReference);
+      }, 0);
+    });
+    otherW.close();
+    assert_equals(otherW[windowProxySelfReference], otherW, `${windowProxySelfReference} got cleared after browsing context closure`);
+    assert_true(otherW.closed);
+  }, `popupWindow.${windowProxySelfReference} before, after closing, and after discarding`)
+});