[Media Router] Parse device description xml in utility process

chrome/common/media_router/dial_device_description_parser.mojom

+// Copyright 2017 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.
+
+// DIAL device description parsing interface provided by the utility process and
+// exposed by mojo policy control to the chrome browser process.
+
+module chrome.mojom;
+
+struct DialDeviceDescription {
+  // UUID (UDN).
+  string unique_id;
+
+  // Short user-friendly title.
+  string friendly_name;
+
+  // Model name.
+  string model_name;
+
+  // The reported device type, e.g. urn:dial-multiscreen-org:device:dial:1
+  string device_type;
+};
+
+interface DialDeviceDescriptionParser {
+  // Parses |device_description_xml_data| to get device description data. If
+  // parsing succeeds, invokes callback with |parse_result| equals to true;
+  // otherwise invokes callback with |parse_result| equals to false.
+  // |device_description|: device description object. Empty if parsing fails.
+  // |logging_xml|: xml file for logging without unique ID and serial number.

[mark a. foltz, 2017/03/21 01:39:21]

Is this empty if result == false?

[zhaobin, 2017/03/21 03:15:37]

Removed :)

+  ParseDialDeviceDescription(string device_description_xml_data)

[mark a. foltz, 2017/03/21 01:39:21]

Another API would be:

=> (bool success, DialDeviceDescription? device_description)
 
with the plan being that |success| is replaced by an enum indicating success or
the failure reason in the future if need be.

This way the service doesn't have to pass an empty (and invalid) description
back on failure.   It's also more consistent with other APIs we maintain that
use optional return values with an error status, like
PresentationService::StartPresentation().

It adds some complexity to the C++ API and that might outweigh any perceived
benefit.  Let me know what you think.

[zhaobin, 2017/03/21 03:15:38]

Done.

+      => (bool parse_result,

[mark a. foltz, 2017/03/21 01:39:21]

s/parse_result/success/ ?

[zhaobin, 2017/03/21 03:15:37]

Done.

+          DialDeviceDescription device_description,
+          string logging_xml);

[mark a. foltz, 2017/03/21 01:39:21]

Could logging_xml be a field in DialDeviceDescription?  Or is it important to
pass it separately?

[mark a. foltz, 2017/03/21 01:41:10]

I realize that passing separately means we can log it in the caller, even if
parsing fails and we don't return a DialDeviceDescription.  So let's keep it
separate :)

[zhaobin, 2017/03/21 03:15:37]

Removed logging related code in this patch. Will add them to DialMediaSink patch
(in future), which uses SafeDialDeviceDescriptionParser.

+};