Resolve FetchEvent.preloadResponse with undefined when Navigation Preload is disabled.

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 b128e2ad765410e26e57557f3b8e99a918c1db05..3333a8a8dfb7534139342ca7972fadbc5acf9979 100644
--- a/content/browser/service_worker/service_worker_browsertest.cc
+++ b/content/browser/service_worker/service_worker_browsertest.cc
@@ -1764,7 +1764,7 @@ IN_PROC_BROWSER_TEST_P(ServiceWorkerNavigationPreloadTest, SetHeaderValue) {
   NavigateToURL(shell(), embedded_test_server()->GetURL(kPageUrl1));
   EXPECT_EQ(title1, title_watcher1.WaitAndGetTitle());
   // When the navigation started, the navigation preload was not enabled yet.
-  EXPECT_EQ("null", GetTextContent());
+  EXPECT_EQ("undefined", GetTextContent());
   ASSERT_EQ(0, GetRequestCount(kPageUrl1));
 
   const std::string kPageUrl2 = kPageUrl + "?change";
@@ -1799,7 +1799,7 @@ IN_PROC_BROWSER_TEST_P(ServiceWorkerNavigationPreloadTest, SetHeaderValue) {
   NavigateToURL(shell(), embedded_test_server()->GetURL(kPageUrl4));
   EXPECT_EQ(title4, title_watcher4.WaitAndGetTitle());
   // When the navigation started, the navigation preload must be disabled.
-  EXPECT_EQ("null", GetTextContent());
+  EXPECT_EQ("undefined", GetTextContent());
   ASSERT_EQ(0, GetRequestCount(kPageUrl4));
 }
 
@@ -2051,7 +2051,7 @@ IN_PROC_BROWSER_TEST_P(ServiceWorkerNavigationPreloadTest, NotEnabled) {
   // The page request must not be sent, since the worker responded with a
   // generated Response and the navigation preload isn't enabled.
   EXPECT_EQ(0, GetRequestCount(kPageUrl));
-  EXPECT_EQ("Resolved with null.", GetTextContent());
+  EXPECT_EQ("Resolved with undefined.", GetTextContent());
 }
 
 IN_PROC_BROWSER_TEST_P(ServiceWorkerNavigationPreloadTest,