Implement break signal for serial api.

device/serial/serial_io_handler_posix.cc

Index: device/serial/serial_io_handler_posix.cc
diff --git a/device/serial/serial_io_handler_posix.cc b/device/serial/serial_io_handler_posix.cc
index 52aad173d397064ef9d9ddf6c54d76d8524b0a3e..fa9bef1ac4f3e84fed767ceb25859efeb62da939 100644
--- a/device/serial/serial_io_handler_posix.cc
+++ b/device/serial/serial_io_handler_posix.cc
@@ -472,6 +472,14 @@ serial::ConnectionInfoPtr SerialIoHandlerPosix::GetPortInfo() const {
   return info.Pass();
 }
 
+bool SerialIoHandlerPosix::SetBreak() {
+  return ioctl(file().GetPlatformFile(), TIOCSBRK, 0) == 0;

[Reilly Grant (use Gerrit), 2015/06/10 19:42:13]

Please catch errors here and use a VPLOG to record them.

[limasdf, 2015/06/11 22:14:24]

Done.

+}
+
+bool SerialIoHandlerPosix::ClearBreak() {
+  return ioctl(file().GetPlatformFile(), TIOCCBRK, 0) == 0;

[Reilly Grant (use Gerrit), 2015/06/10 19:42:13]

Same here.

[limasdf, 2015/06/11 22:14:23]

Done.

+}
+
 std::string SerialIoHandler::MaybeFixUpPortName(const std::string& port_name) {
   return port_name;
 }