Add MessagePipe interface. Use it in ChannelDispatcherBase.

remoting/protocol/message_pipe.h

Index: remoting/protocol/message_pipe.h
diff --git a/remoting/protocol/message_pipe.h b/remoting/protocol/message_pipe.h
new file mode 100644
index 0000000000000000000000000000000000000000..ee24dec572841607249eb00ec67dcd1d19587745
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+++ b/remoting/protocol/message_pipe.h
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+// 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 REMOTING_PROTOCOL_MESSAGE_PIPE_H_
+#define REMOTING_PROTOCOL_MESSAGE_PIPE_H_
+
+#include "base/callback_forward.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace google {
+namespace protobuf {
+class MessageLite;
+}  // namespace protobuf
+}  // namespace google
+
+namespace remoting {
+
+class CompoundBuffer;
+
+namespace protocol {
+
+// Represents a bi-directional pipe that allows to send and receive messages.
+class MessagePipe {
+ public:
+  typedef base::Callback<void(scoped_ptr<CompoundBuffer> message)>
+      MessageReceivedCallback;
+
+  virtual ~MessagePipe() {}
+
+  // Starts receiving incoming messages and calls |callback| for each message.
+  virtual void StartReceiving(const MessageReceivedCallback& callback) = 0;
+
+  // Sends a message.
+  virtual void Send(google::protobuf::MessageLite* message,
+                    const base::Closure& done) = 0;
+};
+
+}  // namespace protocol
+}  // namespace remoting
+
+#endif  // REMOTING_PROTOCOL_MESSAGE_PIPE_H_