Make PacketReader/PacketWriter interfaces async-only.

blimp/net/packet_writer.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 BLIMP_NET_PACKET_WRITER_H_
 #define BLIMP_NET_PACKET_WRITER_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "blimp/net/blimp_net_export.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 namespace blimp {
 
 // Interface to describe a writer which can write variable-length data packets
 // to a connection.
 class BLIMP_NET_EXPORT PacketWriter {
  public:
   virtual ~PacketWriter() {}
 
-  // Writes a packet of at least one byte in size to a connection.
-  //
-  // Returns net::OK or an error code if the operation executed successfully.
-  // Returns ERR_IO_PENDING if the operation will be executed asynchronously.
-  //     |cb| is later invoked with net::OK or an error code.
-  // An error code indicates that caller should stop using this writer.
-  virtual int WritePacket(scoped_refptr<net::DrainableIOBuffer> data,
-                          const net::CompletionCallback& callback) = 0;
+  // Invokes |cb| with net::OK if the write operation executed successfully.
+  // All other values indicate unrecoverable errors.
+  virtual void WritePacket(scoped_refptr<net::DrainableIOBuffer> data,
+                           const net::CompletionCallback& callback) = 0;
 };
 
 }  // namespace blimp
 
 #endif  // BLIMP_NET_PACKET_WRITER_H_