XMLHttpRequest: response stream errors

For whatwg/xhr#314.

service-workers/service-worker/fetch-request-xhr-sync-error.https.window.js

@@ -0,0 +1,19 @@
+// META: script=resources/test-helpers.sub.js
+
+"use strict";
+
+promise_test(async t => {
+  const url = "resources/fetch-request-xhr-sync-error-worker.js";
+  const scope = "resources/fetch-request-xhr-sync-iframe.html";
+
+  const registration = await service_worker_unregister_and_register(t, url, scope);
+  t.add_cleanup(() => registration.unregister());
+
+  await wait_for_state(t, registration.installing, 'activated');
+  const frame = await with_iframe(scope);
+  t.add_cleanup(() => frame.remove());
+
+  assert_throws_dom("NetworkError", frame.contentWindow.DOMException, () => frame.contentWindow.performSyncXHR("non-existent-stream-1.txt"));
+  assert_throws_dom("NetworkError", frame.contentWindow.DOMException, () => frame.contentWindow.performSyncXHR("non-existent-stream-2.txt"));
+  assert_throws_dom("NetworkError", frame.contentWindow.DOMException, () => frame.contentWindow.performSyncXHR("non-existent-stream-3.txt"));
+}, "Verify synchronous XMLHttpRequest always throws a NetworkError for ReadableStream errors");

service-workers/service-worker/resources/fetch-request-xhr-sync-error-worker.js

@@ -0,0 +1,19 @@
+"use strict";
+
+self.onfetch = event => {
+  if (event.request.url.endsWith("non-existent-stream-1.txt")) {
+    const rs1 = new ReadableStream();
+    event.respondWith(new Response(rs1));
+    rs1.cancel(1);
+  } else if (event.request.url.endsWith("non-existent-stream-2.txt")) {
+    const rs2 = new ReadableStream({
+      start(controller) { controller.error(1) }
+    });
+    event.respondWith(new Response(rs2));
+  } else if (event.request.url.endsWith("non-existent-stream-3.txt")) {
+    const rs3 = new ReadableStream({
+      pull(controller) { controller.error(1) }
+    });
+    event.respondWith(new Response(rs3));
+  }
+};