Explicitly initialize secondary renderers for layout tests.

content/shell/browser/layout_test/notify_done_forwarder.h

-// Copyright 2013 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.
-
-#ifndef CONTENT_SHELL_BROWSER_LAYOUT_TEST_NOTIFY_DONE_FORWARDER_H_
-#define CONTENT_SHELL_BROWSER_LAYOUT_TEST_NOTIFY_DONE_FORWARDER_H_
-
-#include "base/macros.h"
-#include "content/public/browser/web_contents_observer.h"
-#include "content/public/browser/web_contents_user_data.h"
-
-namespace content {
-
-class NotifyDoneForwarder : public WebContentsObserver,
-                            public WebContentsUserData<NotifyDoneForwarder> {
- public:
-  ~NotifyDoneForwarder() override;
-
-  // WebContentsObserver implementation.
-  bool OnMessageReceived(const IPC::Message& message) override;
-
- private:
-  friend class WebContentsUserData<NotifyDoneForwarder>;
-
-  explicit NotifyDoneForwarder(WebContents* web_contents);
-
-  void OnTestFinishedInSecondaryRenderer();
-
-  DISALLOW_COPY_AND_ASSIGN(NotifyDoneForwarder);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_SHELL_BROWSER_LAYOUT_TEST_NOTIFY_DONE_FORWARDER_H_