Implement break signal for serial api.

extensions/browser/api/serial/serial_connection.cc

Index: extensions/browser/api/serial/serial_connection.cc
diff --git a/extensions/browser/api/serial/serial_connection.cc b/extensions/browser/api/serial/serial_connection.cc
index ef25885941b28f9cf5f611ca9d260f2d3aae2c82..ebe3f9b5c40e0143c1033870c1a8c70389b324c0 100644
--- a/extensions/browser/api/serial/serial_connection.cc
+++ b/extensions/browser/api/serial/serial_connection.cc
@@ -360,6 +360,14 @@ bool SerialConnection::SetControlSignals(
       *device::serial::HostControlSignals::From(control_signals));
 }
 
+bool SerialConnection::SetBreak() {
+  return io_handler_->SetBreak();
+}
+
+bool SerialConnection::ClearBreak() {
+  return io_handler_->ClearBreak();
+}
+
 void SerialConnection::OnReceiveTimeout() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   io_handler_->CancelRead(device::serial::RECEIVE_ERROR_TIMEOUT);