ipc: Make a common subclass for Channel and ProxyChannel.

ipc/ipc_endpoint.h

+// Copyright 2015 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_ENDPOINT_H_
+#define IPC_IPC_ENDPOINT_H_
+
+#include "base/process/process_handle.h"
+#include "ipc/ipc_export.h"
+#include "ipc/ipc_sender.h"
+
+namespace IPC {
+
+// An Endpoint is an abstract base class whose interface provides sending
+// functionality, and some receiving functionality. It mostly exists to provide
+// a common interface to Channel and ProxyChannel.
+class IPC_EXPORT Endpoint : public Sender {
+ public:
+  Endpoint();
+  ~Endpoint() override {}
+
+  // Get the process ID for the connected peer.
+  //
+  // Returns base::kNullProcessId if the peer is not connected yet. Watch out
+  // for race conditions. You can easily get a channel to another process, but
+  // if your process has not yet processed the "hello" message from the remote
+  // side, this will fail. You should either make sure calling this is either
+  // in response to a message from the remote side (which guarantees that it's
+  // been connected), or you wait for the "connected" notification on the
+  // listener.
+  virtual base::ProcessId GetPeerPID() const = 0;
+
+  // A callback that indicates that is_attachment_broker_endpoint() has been
+  // changed.
+  virtual void OnSetAttachmentBrokerEndpoint(){};
+
+  // Whether this channel is used as an endpoint for sending and receiving
+  // brokerable attachment messages to/from the broker process.
+  void SetAttachmentBrokerEndpoint(bool is_endpoint);
+
+ protected:
+  bool is_attachment_broker_endpoint() { return attachment_broker_endpoint_; }
+
+ private:
+  // Whether this channel is used as an endpoint for sending and receiving
+  // brokerable attachment messages to/from the broker process.
+  bool attachment_broker_endpoint_;
+};
+
+}  // namespace IPC
+
+#endif  // IPC_IPC_ENDPOINT_H_