[battor agent] Add 'read more bytes' logic in the BattOr connection

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>
 
@@ skipping 51 matching lines @@
 
   // Internal callback for when bytes are read. This method may trigger
   // additional reads if any newly read bytes are escape bytes.
   void OnBytesRead(int bytes_read, device::serial::ReceiveError error);
 
   void EndReadBytes(bool success,
                     BattOrMessageType type,
                     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);
+  // its type and contents through out parameters and any error that occurred
+  // through the return value.
+  enum ParseMessageError {
+    NONE = 0,
+    NOT_ENOUGH_BYTES = 1,
+    MISSING_START_BYTE = 2,
+    INVALID_MESSAGE_TYPE = 3,
+    TOO_MANY_START_BYTES = 4
+  };
+
+  ParseMessageError 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_;
 
@@ skipping 13 matching lines @@
   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_