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..91cd110ca3eb6ea49efd2a3efa51fe7b693c267c 100644
--- a/device/serial/serial_io_handler_posix.cc
+++ b/device/serial/serial_io_handler_posix.cc
@@ -472,6 +472,23 @@ serial::ConnectionInfoPtr SerialIoHandlerPosix::GetPortInfo() const {
   return info.Pass();
 }
 
+bool SerialIoHandlerPosix::SetBreak() {
+  if (ioctl(file().GetPlatformFile(), TIOCSBRK, 0) != 0) {
+    VPLOG(1) << "Failed to set break";
+    return false;
+  }
+
+  return true;
+}
+
+bool SerialIoHandlerPosix::ClearBreak() {
+  if (ioctl(file().GetPlatformFile(), TIOCCBRK, 0) != 0) {
+    VPLOG(1) << "Failed to clear break";
+    return false;
+  }
+  return true;
+}
+
 std::string SerialIoHandler::MaybeFixUpPortName(const std::string& port_name) {
   return port_name;
 }