Fix a possible flaky ServiceWorkerNavigationPreloadTest.

content/browser/service_worker/service_worker_browsertest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <utility>
@@ skipping 1615 matching lines @@
   RegisterStaticFile(kWorkerUrl, kScript, "text/javascript");
 
   SetupForNavigationPreloadTest(page_url, worker_url);
 
   const base::string16 title = base::ASCIIToUTF16("PASS");
   TitleWatcher title_watcher(shell()->web_contents(), title);
   NavigateToURL(shell(), page_url);
   EXPECT_EQ(title, title_watcher.WaitAndGetTitle());
   EXPECT_EQ("Hello world.", GetTextContent());
 
-  // The page request must be sent twice. Once for navigation preload, and once
-  // for fallback since respondWith wasn't used.
-  ASSERT_EQ(2, GetRequestCount(kPageUrl));
-  ASSERT_TRUE(HasNavigationPreloadHeader(request_log_[kPageUrl][0]));
-  EXPECT_EQ("true", GetNavigationPreloadHeader(request_log_[kPageUrl][0]));
-  EXPECT_FALSE(HasNavigationPreloadHeader(request_log_[kPageUrl][1]));
+  // The page request must be sent once or twice:
+  // - A navigation preload request may be sent. But it is possible that the
+  //   navigation preload request is canceled before reaching the server.
+  // - A fallback request must be sent since respondWith wasn't used.
+  const int request_count = GetRequestCount(kPageUrl);
+  ASSERT_TRUE(request_count == 1 || request_count == 2);
+  if (request_count == 1) {
+    // Fallback request.
+    EXPECT_FALSE(HasNavigationPreloadHeader(request_log_[kPageUrl][0]));
+  } else if (request_count == 2) {
+    // Navigation preload request.
+    ASSERT_TRUE(HasNavigationPreloadHeader(request_log_[kPageUrl][0]));
+    EXPECT_EQ("true", GetNavigationPreloadHeader(request_log_[kPageUrl][0]));
+    // Fallback request.
+    EXPECT_FALSE(HasNavigationPreloadHeader(request_log_[kPageUrl][1]));
+  }
 }
 
 IN_PROC_BROWSER_TEST_P(ServiceWorkerNavigationPreloadTest, SetHeaderValue) {
   const std::string kPageUrl = "/service_worker/navigation_preload.html";
   const std::string kWorkerUrl = "/service_worker/navigation_preload.js";
   const std::string kPage = "<title>FROM_SERVER</title>";
   const std::string kScript =
       "function createResponse(title, body) {\n"
       "  return new Response('<title>' + title + '</title>' + body,\n"
       "                      {headers: [['content-type', 'text/html']]})\n"
@@ skipping 1185 matching lines @@
                         ServiceWorkerV8CacheStrategiesNormalTest,
                         ::testing::Values(true, false));
 INSTANTIATE_TEST_CASE_P(ServiceWorkerBrowserTest,
                         ServiceWorkerV8CacheStrategiesAggressiveTest,
                         ::testing::Values(true, false));
 INSTANTIATE_TEST_CASE_P(ServiceWorkerBrowserTest,
                         ServiceWorkerDisableWebSecurityTest,
                         ::testing::Values(true, false));
 
 }  // namespace content