Fix potential flakiness in PrerenderBrowserTest.AutosigninInPrerenderer

chrome/browser/prerender/prerender_browsertest.cc

 // Copyright (c) 2012 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 <deque>
 #include <set>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ skipping 3232 matching lines @@
   // It should never load as the API is suppressed.
   GURL done_url = embedded_test_server()->GetURL("/password/done.html");
   base::FilePath empty_file = ui_test_utils::GetTestFilePath(
       base::FilePath(), base::FilePath(FILE_PATH_LITERAL("empty.html")));
   RequestCounter done_counter;
   BrowserThread::PostTask(
       BrowserThread::IO, FROM_HERE,
       base::Bind(&CreateCountingInterceptorOnIO,
                  done_url, empty_file, done_counter.AsWeakPtr()));
   // Loading may finish or be interrupted. The final result is important only.
-  // TODO(http://crbug.com/660278): TestPrrenderContents can be created after
-  // the JS code runs. The result would be a test timeout.
   DisableLoadEventCheck();
+  // TestPrenderContents is always created before the Autosignin JS can run, so
+  // waiting for PrerenderContents to stop should be reliable.
   PrerenderTestURL("/password/autosignin.html",
                    FINAL_STATUS_CREDENTIAL_MANAGER_API, 0);
   EXPECT_EQ(0, done_counter.count());
 }
 
 class PrerenderIncognitoBrowserTest : public PrerenderBrowserTest {
  public:
   void SetUpOnMainThread() override {
     Profile* normal_profile = current_browser()->profile();
     set_browser(OpenURLOffTheRecord(normal_profile, GURL("about:blank")));
@@ skipping 140 matching lines @@
       browser()->tab_strip_model()->GetActiveWebContents();
   bool display_test_result = false;
   ASSERT_TRUE(content::ExecuteScriptAndExtractBool(web_contents,
                                                    "DidDisplayReallyPass()",
                                                    &display_test_result));
   ASSERT_TRUE(display_test_result);
 }
 #endif  // !defined(DISABLE_NACL)
 
 }  // namespace prerender