Add a partial Mojo serial connection interface and implementation.

device/serial/BUILD.gn

 # 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 # GYP version: device/serial/serial.gyp:device_serial
 static_library("serial") {
   output_name = "device_serial"
 
   sources = [
+    "serial_connection.cc",
+    "serial_connection.h",
+    "serial_connection_factory.cc",
+    "serial_connection_factory.h",
     "serial_device_enumerator.cc",
     "serial_device_enumerator.h",
     "serial_device_enumerator_linux.cc",
     "serial_device_enumerator_linux.h",
     "serial_device_enumerator_mac.cc",
     "serial_device_enumerator_mac.h",
     "serial_device_enumerator_win.cc",
     "serial_device_enumerator_win.h",
+    "serial_io_handler.cc",
+    "serial_io_handler.h",
+    "serial_io_handler_posix.cc",
+    "serial_io_handler_posix.h",
+    "serial_io_handler_win.cc",
+    "serial_io_handler_win.h",
+    "serial_service_impl.cc",
+    "serial_service_impl.h",
   ]
 
   if (is_linux) {
     configs += [ "//build/config/linux:udev" ]
   }
 
   deps = [
     ":serial_mojo",
   ]
 }
 
+# GYP version: device/serial/serial.gyp:device_serial_test_util
+static_library("test_util") {
+  output_name = "device_serial_test_util"
+
+  sources = [
+    "test_serial_io_handler.cc",
+    "test_serial_io_handler.h",
+  ]
+
+  deps = [
+    ":serial",
+  ]
+}
+
 mojom("serial_mojo") {
   visibility = ":serial"
 
   sources = [
     "serial.mojom",
   ]
 }