Convert SerialDeviceInfo to a Mojo struct.

device/serial/serial.mojom

Index: device/serial/serial.mojom
diff --git a/device/serial/serial.mojom b/device/serial/serial.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..f925dff33cd1b32c622e5b783057893c7c262379
--- /dev/null
+++ b/device/serial/serial.mojom
@@ -0,0 +1,16 @@
+// 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 {
+
+struct SerialDeviceInfo {
+  string path;
+  uint16 vendor_id;
+  bool has_vendor_id = false;
+  uint16 product_id;
+  bool has_product_id = false;
+  string display_name;
+};
+
+}