[mojo-edk] Simplify multiprocess pipe bootstrap

mojo/edk/system/remote_message_pipe_bootstrap.h

 // Copyright 2016 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 MOJO_EDK_SYSTEM_REMOTE_MESSAGE_PIPE_BOOTSTRAP_H_
 #define MOJO_EDK_SYSTEM_REMOTE_MESSAGE_PIPE_BOOTSTRAP_H_
 
 #include <string>
 
-#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
 #include "base/task_runner.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "mojo/edk/system/channel.h"
 #include "mojo/edk/system/ports/name.h"
 #include "mojo/edk/system/ports/port_ref.h"
 
 namespace mojo {
 namespace edk {
 
 class NodeController;
 
 // This is used by Core to negotiate a new cross-process message pipe given
 // an arbitrary platform channel. Both ends of the channel must be passed to
 // RemoteMessagePipeBootstrap::Create() in their respective processes.
 //
 // The bootstrapping procedure the same on either end:
 //
-//   1. Create a local port P.
+//   1. Select a local port P to be merged with a remote port.
 //   2. Write the local node name and P's name to the bootstrap pipe.
 //   3. When a message is read from the pipe:
 //      - If it's the first message read, extract the remote node+port name and
-//        initialize the local port. Send an empty ACK message on the pipe.
+//        and send an empty ACK message on the pipe.
 //      - If it's the second message read, close the channel, and delete |this|.
 //   4. When an error occus on the pipe, delete |this|.
 //
 // Excluding irrecoverable error conditions such as either process dying,
 // armageddon, etc., this ensures neither end closes the channel until both ends
-// have intiailized their corresponding local port.
+// are aware of each other's port-to-merge.
+//
+// At step 3, one side of the channel is chosen to issue a message at the Ports
+// layer which eventually merges the two ports.
 class RemoteMessagePipeBootstrap
     : public Channel::Delegate,
       public base::MessageLoop::DestructionObserver {
  public:
   ~RemoteMessagePipeBootstrap() override;
 
   // |port| must be a reference to an uninitialized local port.
   static void Create(NodeController* node_controller,
                      ScopedPlatformHandle platform_handle,
-                     const ports::PortRef& port,
-                     const base::Closure& callback);
+                     const ports::PortRef& port);
 
  protected:
-  explicit RemoteMessagePipeBootstrap(
-      NodeController* node_controller,
-      ScopedPlatformHandle platform_handle,
-      const ports::PortRef& port,
-      const base::Closure& callback);
+  explicit RemoteMessagePipeBootstrap(NodeController* node_controller,
+                                      ScopedPlatformHandle platform_handle,
+                                      const ports::PortRef& port);
 
   void ShutDown();
 
   bool shutting_down_ = false;
   NodeController* node_controller_;
   const ports::PortRef local_port_;
-  base::Closure callback_;
 
   scoped_refptr<base::TaskRunner> io_task_runner_;
   scoped_refptr<Channel> channel_;
 
   bool peer_info_received_ = false;
 
  private:
   // base::MessageLoop::DestructionObserver:
   void WillDestroyCurrentMessageLoop() override;
 
   // Channel::Delegate:
   void OnChannelMessage(const void* payload,
                         size_t payload_size,
                         ScopedPlatformHandleVectorPtr handles) override;
   void OnChannelError() override;
 
   void ShutDownNow();
 
   DISALLOW_COPY_AND_ASSIGN(RemoteMessagePipeBootstrap);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_REMOTE_MESSAGE_PIPE_BOOTSTRAP_H_