Add a partial Mojo serial connection interface and implementation.

device/serial/serial.mojom

 // 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.
 
 module device.serial {
 
 struct DeviceInfo {
   string path;
   uint16 vendor_id;
   bool has_vendor_id = false;
@@ skipping 63 matching lines @@
 
 struct DeviceControlSignals {
   bool dcd;
   bool cts;
   bool ri;
   bool dsr;
 };
 
 interface SerialService {
   GetDevices() => (DeviceInfo[] devices);
+
+  // Creates a |Connection| to |path| with options specified by |options|,
+  // returning it via |connection|. This will fail and |connection| will not be
+  // usable if |path| does not specify a valid serial device or there is an
+  // error connecting to or configuring the connection.
+  Connect(string path,
+          ConnectionOptions options,
+          Connection& connection);
+};
+
+interface Connection {
+  GetInfo() => (ConnectionInfo info);
+  SetOptions(ConnectionOptions options) => (bool success);
+  SetControlSignals(HostControlSignals signals) => (bool success);
+  GetControlSignals() => (DeviceControlSignals signals);
+  Flush() => (bool success);
 };
 
 }