Explicitly put serial port fd in non-blocking mode on Chrome OS.

device/serial/serial_io_handler_posix.h

 // Copyright 2014 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 DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
 #define DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
 
 #include <memory>
 
 #include "base/files/file_descriptor_watcher_posix.h"
@@ skipping 10 matching lines @@
 enum class ErrorDetectState { NO_ERROR, MARK_377_SEEN, MARK_0_SEEN };
 
 class SerialIoHandlerPosix : public SerialIoHandler {
  protected:
   // SerialIoHandler impl.
   void ReadImpl() override;
   void WriteImpl() override;
   void CancelReadImpl() override;
   void CancelWriteImpl() override;
   bool ConfigurePortImpl() override;
+  bool PostOpen() override;
   bool Flush() const override;
   serial::DeviceControlSignalsPtr GetControlSignals() const override;
   bool SetControlSignals(
       const serial::HostControlSignals& control_signals) override;
   serial::ConnectionInfoPtr GetPortInfo() const override;
   bool SetBreak() override;
   bool ClearBreak() override;
   int CheckReceiveError(char* buffer,
                         int buffer_len,
                         int bytes_read,
@@ skipping 27 matching lines @@
   bool parity_check_enabled_;
   char chars_stashed_[2];
   int num_chars_stashed_;
 
   DISALLOW_COPY_AND_ASSIGN(SerialIoHandlerPosix);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_