ipc: Use a global for the process's attachment broker.

ipc/ipc_channel_posix.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 IPC_IPC_CHANNEL_POSIX_H_
 #define IPC_IPC_CHANNEL_POSIX_H_
 
 #include "ipc/ipc_channel.h"
 
 #include <sys/socket.h>  // for CMSG macros
@@ skipping 11 matching lines @@
 
 namespace IPC {
 
 class IPC_EXPORT ChannelPosix : public Channel,
                                 public internal::ChannelReader,
                                 public base::MessageLoopForIO::Watcher {
  public:
   // |broker| must outlive the newly created object.
   ChannelPosix(const IPC::ChannelHandle& channel_handle,
                Mode mode,
-               Listener* listener,
-               AttachmentBroker* broker);
+               Listener* listener);
   ~ChannelPosix() override;
 
   // Channel implementation
   bool Connect() override;
   void Close() override;
   bool Send(Message* message) override;
   AttachmentBroker* GetAttachmentBroker() override;
   base::ProcessId GetPeerPID() const override;
   base::ProcessId GetSelfPID() const override;
   int GetClientFileDescriptor() const override;
@@ skipping 131 matching lines @@
 #endif
 
   // True if we are responsible for unlinking the unix domain socket file.
   bool must_unlink_;
 
 #if defined(OS_LINUX)
   // If non-zero, overrides the process ID sent in the hello message.
   static int global_pid_;
 #endif  // OS_LINUX
 
-  // |broker_| must outlive this instance.
-  AttachmentBroker* broker_;
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelPosix);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_CHANNEL_POSIX_H_