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

device/serial/serial_io_handler.cc

Index: device/serial/serial_io_handler.cc
diff --git a/device/serial/serial_io_handler.cc b/device/serial/serial_io_handler.cc
index 82fa34342524e8287abdd754eb05b808cc873bd2..c037ea79491768639725cf753c9be750f5086247 100644
--- a/device/serial/serial_io_handler.cc
+++ b/device/serial/serial_io_handler.cc
@@ -158,9 +158,8 @@ void SerialIoHandler::FinishOpen(base::File file) {
   file_ = std::move(file);
 
   bool success = PostOpen() && ConfigurePortImpl();
-  if (!success) {
+  if (!success)
     Close();
-  }
 
   callback.Run(success);
 }