[battor agent] Add option to log serial communication

tools/battor_agent/battor_connection_impl.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 TOOLS_BATTOR_AGENT_BATTOR_CONNECTION_IMPL_H_
 #define TOOLS_BATTOR_AGENT_BATTOR_CONNECTION_IMPL_H_
 
+#include <fstream>
 #include <vector>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "device/serial/serial.mojom.h"
 #include "tools/battor_agent/battor_connection.h"
 #include "tools/battor_agent/battor_error.h"
 #include "tools/battor_agent/battor_protocol_types.h"
@@ skipping 50 matching lines @@
                     std::unique_ptr<std::vector<char>> data);
 
   // Pulls off the next complete message from already_read_buffer_, returning
   // its type and contents (via out parameters) and whether a complete message
   // was able to be read (via the return value).
   bool ParseMessage(BattOrMessageType* type, std::vector<char>* data);
 
   // Internal callback for when bytes are sent.
   void OnBytesSent(int bytes_sent, device::serial::SendError error);
 
+  // Appends |str| to the serial log file if it exists.
+  void LogSerial(const std::string& str);
+
   // The path of the BattOr.
   std::string path_;
 
   // All bytes that have already been read from the serial stream, but have not
   // yet been given to the listener as a complete message.
   std::vector<char> already_read_buffer_;
   // The bytes that were read in the pending read.
   scoped_refptr<net::IOBuffer> pending_read_buffer_;
   // The type of message we're looking for in the pending read.
   BattOrMessageType pending_read_message_type_;
 
   // The total number of bytes that we're expecting to send.
   size_t pending_write_length_;
 
   // Threads needed for serial communication.
   scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner_;
 
+  std::fstream serial_log_;
+
   DISALLOW_COPY_AND_ASSIGN(BattOrConnectionImpl);
 };
 
 }  // namespace battor
 
 #endif  // TOOLS_BATTOR_AGENT_BATTOR_CONNECTION_IMPL_H_