Always disable the beforeunload timer when injecting the beforeunload method.

chrome/browser/devtools/devtools_sanity_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 <memory>
 
 #include "base/bind.h"
 #include "base/cancelable_callback.h"
@@ skipping 364 matching lines @@
 
   void CloseInspectedBrowser() {
     chrome::CloseWindow(browser());
   }
 
  protected:
   void InjectBeforeUnloadListener(content::WebContents* web_contents) {
     ASSERT_TRUE(content::ExecuteScript(web_contents->GetRenderViewHost(),
         "window.addEventListener('beforeunload',"
         "function(event) { event.returnValue = 'Foo'; });"));
+    // Disable the hang monitor, otherwise there will be a race between the
+    // beforeunload dialog and the beforeunload hang timer.
+    web_contents->GetMainFrame()->DisableBeforeUnloadHangMonitorForTesting();
   }
 
   void RunBeforeUnloadSanityTest(bool is_docked,
                                  base::Callback<void(void)> close_method,
                                  bool wait_for_browser_close = true) {
     OpenDevToolsWindow(kDebuggerTestPage, is_docked);
     scoped_refptr<content::MessageLoopRunner> runner =
         new content::MessageLoopRunner;
     DevToolsWindowTesting::Get(window_)->
         SetCloseCallback(runner->QuitClosure());
     InjectBeforeUnloadListener(main_web_contents());
-    main_web_contents()
-        ->GetMainFrame()
-        ->DisableBeforeUnloadHangMonitorForTesting();
     {
       DevToolsWindowBeforeUnloadObserver before_unload_observer(window_);
       close_method.Run();
       CancelModalDialog();
       before_unload_observer.Wait();
     }
     {
       content::WindowedNotificationObserver close_observer(
           chrome::NOTIFICATION_BROWSER_CLOSED,
           content::Source<Browser>(browser()));
@@ skipping 405 matching lines @@
                     DevToolsWindowTesting::Get(devtools_window)->
                         main_web_contents()));
     close_observers.push_back(close_observer);
     inspected_web_contents =
         DevToolsWindowTesting::Get(devtools_window)->main_web_contents();
   }
 
   InjectBeforeUnloadListener(
       DevToolsWindowTesting::Get(windows[0])->main_web_contents());
   InjectBeforeUnloadListener(
       DevToolsWindowTesting::Get(windows[2])->main_web_contents());

[Avi (use Gerrit), 2017/03/30 15:29:58]

This is the second spot where InjectBeforeUnloadListener() is called. Putting
the timeout kill into InjectBeforeUnloadListener() fixes this test too.

   // Try to close second devtools.
   {
     content::WindowedNotificationObserver cancel_browser(
         chrome::NOTIFICATION_BROWSER_CLOSE_CANCELLED,
         content::NotificationService::AllSources());
     chrome::CloseWindow(DevToolsWindowTesting::Get(windows[1])->browser());
     CancelModalDialog();
     cancel_browser.Wait();
   }
   // Try to close browser window.
@@ skipping 706 matching lines @@
   RunTestFunction(window, "testWindowInitializedOnNavigateBack");
 
   DevToolsWindowTesting::CloseDevToolsWindowSync(window);
   content::WebUIControllerFactory::UnregisterFactoryForTesting(&test_factory);
 }
 
 // Tests scripts panel showing.
 IN_PROC_BROWSER_TEST_F(DevToolsSanityTest, TestDevToolsSharedWorker) {
   RunTest("testDevToolsSharedWorker", url::kAboutBlankURL);
 }