Don't make classes derive from ChildProcessHost, and instead have them use it through composition...

content/public/common/child_process_host_delegate.h

+// Copyright (c) 2011 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_PULIC_COMMON_CHILD_PROCESS_HOST_DELEGATE_H_
+#define CONTENT_PULIC_COMMON_CHILD_PROCESS_HOST_DELEGATE_H_
+#pragma once
+
+#include <string>
+
+#include "ipc/ipc_channel.h"
+
+namespace content {
+
+// Interface that all users of ChildProcessHost need to provide.
+class ChildProcessHostDelegate : public IPC::Channel::Listener {
+ public:
+  virtual ~ChildProcessHostDelegate() {}
+
+  // Derived classes return true if it's ok to shut down the child process.
+  // Normally they would return true. The exception is if the host is in the
+  // middle of sending a request to the process, in which case the other side
+  // might think it's ok to shutdown, when really it's not.
+  virtual bool CanShutdown() = 0;
+
+  // Notifies the derived class that we told the child process to kill itself.
+  virtual void ShutdownStarted() = 0;
+
+  // Called when the child process unexpected closes the IPC channel. Delegates
+  // would normally delete the object in this case.
+  virtual void OnChildDisconnected() = 0;
+};
+
+};  // namespace content
+
+#endif  // CONTENT_PULIC_COMMON_CHILD_PROCESS_HOST_DELEGATE_H_