Consolidate the update_client serialization code.

components/update_client/protocol_builder.h

+// 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.
+
+#ifndef COMPONENTS_UPDATE_CLIENT_PROTOCOL_BUILDER_H_
+#define COMPONENTS_UPDATE_CLIENT_PROTOCOL_BUILDER_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "components/update_client/component.h"
+#include "components/update_client/updater_state.h"
+
+namespace update_client {
+
+class Configurator;
+class PersistedData;
+
+// Builds an update check request for |components|. |additional_attributes| is
+// serialized as part of the <request> element of the request to customize it
+// with data that is not platform or component specific. For each |item|, a
+// corresponding <app> element is created and inserted as a child node of
+// the <request>.
+//
+// An app element looks like this:
+//    <app appid="hnimpnehoodheedghdeeijklkeaacbdc"
+//         version="0.1.2.3" installsource="ondemand">
+//      <updatecheck/>
+//      <packages>
+//        <package fp="abcd"/>
+//      </packages>
+//    </app>
+std::string BuildUpdateCheckRequest(
+    const Configurator& config,
+    const std::vector<std::string>& ids_checked,
+    const IdToComponentPtrMap& components,
+    PersistedData* metadata,
+    const std::string& additional_attributes,
+    bool enabled_component_updates,
+    const std::unique_ptr<UpdaterState::Attributes>& updater_state_attributes);
+
+// Builds a ping request for the specified component.

[waffles, 2017/05/17 23:58:05]

Worth documenting what "an event ping request element looks like..." as is done
for the other functions here?

[Sorin Jianu, 2017/05/18 00:25:08]

Done.

+std::string BuildPing(const Configurator& config, const Component& component);

[waffles, 2017/05/17 23:58:05]

BuildPingRequest to match BuildUpdateCheckRequest?

Or, since I always get tripped up that "BuildPing" does not create a <ping>
(instead an <app> with an <event>), maybe BuildEventPingRequest?

[Sorin Jianu, 2017/05/18 00:25:08]

Done.

+
+// An update protocol request starts with a common preamble which includes
+// version and platform information for Chrome and the operating system,
+// followed by a request body, which is the actual payload of the request.
+// For example:
+//
+// <?xml version="1.0" encoding="UTF-8"?>
+// <request protocol="3.0" version="chrome-32.0.1.0" prodversion="32.0.1.0"
+//        requestid="{7383396D-B4DD-46E1-9104-AAC6B918E792}"
+//        updaterchannel="canary" arch="x86" nacl_arch="x86-64"
+//        ADDITIONAL ATTRIBUTES>
+//   <hw physmemory="16"/>
+//   <os platform="win" version="6.1" arch="x86"/>
+//   ... REQUEST BODY ...
+// </request>
+
+// Builds a protocol request string by creating the outer envelope for
+// the request and including the request body specified as a parameter.
+// If present, the |download_preference| specifies a group policy that
+// affects the list of download URLs returned in the update response.
+// If specified, |additional_attributes| are appended as attributes of the
+// request element. The additional attributes have to be well-formed for
+// insertion in the request element. |updater_state_attributes| is an optional
+// parameter specifying that an <updater> element is serialized as part of
+// the request.
+std::string BuildProtocolRequest(
+    const std::string& prod_id,
+    const std::string& browser_version,
+    const std::string& channel,
+    const std::string& lang,
+    const std::string& os_long_name,
+    const std::string& download_preference,
+    const std::string& request_body,
+    const std::string& additional_attributes,
+    const std::unique_ptr<UpdaterState::Attributes>& updater_state_attributes);
+
+}  // namespace update_client
+
+#endif  // COMPONENTS_UPDATE_CLIENT_PROTOCOL_PARSER_H_