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

device/serial/serial_io_handler_posix.cc

 // 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.
 
 #include "device/serial/serial_io_handler_posix.h"
 
 #include <sys/ioctl.h>
 #include <termios.h>
 
+#include "base/files/file_util.h"
 #include "base/posix/eintr_wrapper.h"
 #include "build/build_config.h"
 
 #if defined(OS_LINUX)
 #include <linux/serial.h>
 
 // The definition of struct termios2 is copied from asm-generic/termbits.h
 // because including that header directly conflicts with termios.h.
 extern "C" {
 struct termios2 {
@@ skipping 254 matching lines @@
     if (ioctl(file().GetPlatformFile(), IOSSIOSPEED, &bitrate) == -1) {
       VPLOG(1) << "Failed to set custom baud rate";
       return false;
     }
   }
 #endif
 
   return true;
 }
 
+bool SerialIoHandlerPosix::PostOpen() {
+#if defined(OS_CHROMEOS)
+  // The Chrome OS permission broker does not open devices in async mode.
+  return base::SetNonBlocking(file().GetPlatformFile());
+#else
+  return true;
+#endif
+}
+
 SerialIoHandlerPosix::SerialIoHandlerPosix(
     scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner)
     : SerialIoHandler(file_thread_task_runner, ui_thread_task_runner) {}
 
 SerialIoHandlerPosix::~SerialIoHandlerPosix() {
 }
 
 void SerialIoHandlerPosix::AttemptRead(bool within_read) {
   DCHECK(CalledOnValidThread());
@@ skipping 327 matching lines @@
   memcpy(buffer, chars_stashed_, std::min(new_bytes_read, 2));
   memcpy(chars_stashed_, tmp, num_chars_stashed_);
   return new_bytes_read;
 }
 
 std::string SerialIoHandler::MaybeFixUpPortName(const std::string& port_name) {
   return port_name;
 }
 
 }  // namespace device