Child thread attachment broker should never be destroyed.

content/child/child_thread_impl.h

 // 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.
 
 #ifndef CONTENT_CHILD_CHILD_THREAD_IMPL_H_
 #define CONTENT_CHILD_CHILD_THREAD_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 222 matching lines @@
 #ifdef IPC_MESSAGE_LOG_ENABLED
   void OnSetIPCLoggingEnabled(bool enable);
 #endif
 
   void EnsureConnected();
 
   scoped_ptr<IPC::ScopedIPCSupport> mojo_ipc_support_;
   scoped_ptr<MojoApplication> mojo_application_;
 
   std::string channel_name_;
-  scoped_ptr<IPC::AttachmentBrokerUnprivileged> attachment_broker_;
+  IPC::AttachmentBrokerUnprivileged* attachment_broker_ = nullptr;
   scoped_ptr<IPC::SyncChannel> channel_;
 
   // Allows threads other than the main thread to send sync messages.
   scoped_refptr<IPC::SyncMessageFilter> sync_message_filter_;
 
   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
 
   // Implements message routing functionality to the consumers of
   // ChildThreadImpl.
   ChildThreadMessageRouter router_;
@@ skipping 72 matching lines @@
 
  private:
   struct Options options_;
 
   DISALLOW_COPY_AND_ASSIGN(Builder);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_CHILD_THREAD_IMPL_H_