Make PacketReader/PacketWriter interfaces async-only.

blimp/net/packet_reader.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_READER_H_
 #define BLIMP_NET_PACKET_READER_H_
 
 #include "blimp/net/blimp_net_export.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 
 namespace blimp {
 
 // Interface to describe a reader which can read variable-length data packets
 // from a connection.
 class BLIMP_NET_EXPORT PacketReader {
  public:
   virtual ~PacketReader() {}
 
   // Reads a packet from the connection.
-  // Returns the size of the packet, in bytes, if the read operation executed
-  // successfully.
-  // Returns ERR_IO_PENDING if the operation will be executed asynchronously.
-  //     |cb| is later invoked with the packet size or an error code.
-  // All other return values indicate errors and caller should stop using this
-  // reader.
-  virtual int ReadPacket(const scoped_refptr<net::GrowableIOBuffer>& buf,
-                         const net::CompletionCallback& cb) = 0;
+  // Passes net::OK to |cb| if the read operation executed successfully.
+  // Sets |buf.offset()| to the received message's size, and invokes |cb| with
+  // net::OK result on success.
+  // All other values indicate errors.
+  // |callback| will not be invoked if |this| is deleted.
+  virtual void ReadPacket(const scoped_refptr<net::GrowableIOBuffer>& buf,
+                          const net::CompletionCallback& cb) = 0;
 };
 
 }  // namespace blimp
 
 #endif  // BLIMP_NET_PACKET_READER_H_