Only show a beforeunload dialog if a frame has had a user gesture since its load.

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 <vector>
 
 #include "base/bind.h"
@@ skipping 370 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();
+    content::PrepContentsForBeforeUnloadTest(web_contents);
   }
 
   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());
@@ skipping 1670 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);
 }