Make SubresourceFilterBrowserTest.FailedProvisionalLoadInMainframe non-flaky.

chrome/browser/subresource_filter/subresource_filter_browsertest.cc

Index: chrome/browser/subresource_filter/subresource_filter_browsertest.cc
diff --git a/chrome/browser/subresource_filter/subresource_filter_browsertest.cc b/chrome/browser/subresource_filter/subresource_filter_browsertest.cc
index 73312ad27fe43f352030f66c5c17c35d0ee10255..d41cbab11b67390fc66487900fd9662df8e2f5d4 100644
--- a/chrome/browser/subresource_filter/subresource_filter_browsertest.cc
+++ b/chrome/browser/subresource_filter/subresource_filter_browsertest.cc
@@ -523,13 +523,7 @@ IN_PROC_BROWSER_TEST_F(SubresourceFilterBrowserTest,
                        FailedProvisionalLoadInMainframe) {
   GURL url_with_activation_but_dns_error(
       "http://host-with-dns-lookup-failure/");
-  // The /echo handler returns a 404 with a non-empty response body (containing
-  // the text 'Echo`). The latter is important to suppress showing Chrome's own
-  // navigation error page, in which case a background request is started to
-  // load navigation corrections (aka. Link Doctor), and once the results are
-  // back, there is a navigation to a second error page with the suggestions,
-  // which makes WaitForLoadStop() in the second NavigateToURL() below racey.
-  GURL url_with_activation_but_not_existent(GetTestUrl("/echo?status=404"));
+  GURL url_with_activation_but_not_existent(GetTestUrl("non-existent.html"));
   GURL url_without_activation(GetTestUrl(kTestFrameSetPath));
 
   ConfigureAsPhishingURL(url_with_activation_but_dns_error);
@@ -545,7 +539,13 @@ IN_PROC_BROWSER_TEST_F(SubresourceFilterBrowserTest,
         url_with_activation_but_not_existent}) {
     SCOPED_TRACE(url_with_activation);
 
-    ui_test_utils::NavigateToURL(browser(), url_with_activation);
+    // In either test case, there is no server-supplied error page, so Chrome's
+    // own navigation error page is shown. This also triggers a background
+    // request to load navigation corrections (aka. Link Doctor), and once the
+    // results are back, there is a navigation to a second error page with the
+    // suggestions. Hence the wait for two navigations in a row.
+    ui_test_utils::NavigateToURLBlockUntilNavigationsComplete(
+        browser(), url_with_activation, 2);
     ui_test_utils::NavigateToURL(browser(), url_without_activation);
     ASSERT_NO_FATAL_FAILURE(ExpectParsedScriptElementLoadedStatusInFrames(
         kSubframeNames, kExpectScriptInFrameToLoad));