Add a partial Mojo serial connection interface and implementation.

device/serial/serial.mojom

Index: device/serial/serial.mojom
diff --git a/device/serial/serial.mojom b/device/serial/serial.mojom
index 0c4f1003312479044fd0a96153782155c36258aa..3a788c26951cbfdaf117cdf1ab17a79a5efdadf4 100644
--- a/device/serial/serial.mojom
+++ b/device/serial/serial.mojom
@@ -81,6 +81,17 @@ struct DeviceControlSignals {
 
 interface SerialService {
   GetDevices() => (DeviceInfo[] devices);
+  Connect(string path,
+          ConnectionOptions options,
+          Connection& connection_request);

[darin (slow to review), 2014/07/18 04:46:15]

nit: stylistically, i think it is OK to call this parameter just "connection".
you could think of it as you are connecting the connection object to the serial
service.

[Sam McNally, 2014/07/21 03:25:37]

Done.

+};
+
+interface Connection {
+  GetInfo() => (ConnectionInfo info);
+  SetOptions(ConnectionOptions options) => (bool success);
+  SetControlSignals(HostControlSignals signals) => (bool success);
+  GetControlSignals() => (DeviceControlSignals signals);
+  Flush() => (bool success);
 };
 
 }