Add WARN_UNUSED_RESULT to bool EmbeddedTestServer::Start()

content/browser/service_worker/service_worker_browsertest.cc

Index: content/browser/service_worker/service_worker_browsertest.cc
diff --git a/content/browser/service_worker/service_worker_browsertest.cc b/content/browser/service_worker/service_worker_browsertest.cc
index 45c147c065bab3eb28df900a78a549730d0fb8b2..5e917c3a683c1592666cc35af15670433c42489c 100644
--- a/content/browser/service_worker/service_worker_browsertest.cc
+++ b/content/browser/service_worker/service_worker_browsertest.cc
@@ -1168,7 +1168,7 @@ IN_PROC_BROWSER_TEST_F(ServiceWorkerBrowserTest, CrossOriginFetchWithSaveData) {
   cross_origin_server.ServeFilesFromSourceDirectory("content/test/data");
   cross_origin_server.RegisterRequestHandler(
       base::Bind(&VerifySaveDataNotInAccessControlRequestHeader));
-  cross_origin_server.Start();
+  ASSERT_TRUE(cross_origin_server.Start());
 
   MockContentBrowserClient content_browser_client;
   content_browser_client.set_data_saver_enabled(true);