With --isolate-extensions, forking (via OpenURL) for extensions is not needed.

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 23 matching lines @@
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/test_extension_dir.h"
 #include "chrome/browser/extensions/unpacked_installer.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
-#include "chrome/common/extensions/extension_process_policy.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/test_chrome_web_ui_controller_factory.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "components/app_modal/javascript_app_modal_dialog.h"
 #include "components/app_modal/native_app_modal_dialog.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/child_process_data.h"
 #include "content/public/browser/content_browser_client.h"
@@ skipping 2017 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);
 }