Use udev for serial device enumeration on Linux

device/serial/serial_device_enumerator.cc

Index: device/serial/serial_device_enumerator.cc
diff --git a/device/serial/serial_device_enumerator.cc b/device/serial/serial_device_enumerator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..586d33d8446698e51911ab9cabfc7b4738e1e042
--- /dev/null
+++ b/device/serial/serial_device_enumerator.cc
@@ -0,0 +1,13 @@
+// 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.
+
+#include "device/serial/serial_device_enumerator.h"
+
+namespace device {
+
+SerialDeviceEnumerator::SerialDeviceEnumerator() {}
+
+SerialDeviceEnumerator::~SerialDeviceEnumerator() {}
+
+}  // namespace device