[Chromoting] Implement HostExperimentSessionPlugin

HostExperimentSessionPlugin is a host side SessionPlugin to send host attributes
to, and receive configuration from the client side.
A host can attach this plugin to the Session and use its configuration to
initialize a HostSessionOptions.

This is part of host experiment framework.

BUG=650926

Review-Url: https://codereview.chromium.org/2586133002
Cr-Commit-Position: refs/heads/master@{#441850}

remoting/host/BUILD.gn

@@ -162,6 +162,8 @@ static_library("host") {
     "host_event_logger_win.cc",
     "host_exit_codes.cc",
     "host_exit_codes.h",
+    "host_experiment_session_plugin.cc",
+    "host_experiment_session_plugin.h",
     "host_export.h",
     "host_extension.h",
     "host_extension_session.h",
@@ -498,6 +500,7 @@ source_set("unit_tests") {
     "host_attributes_unittest.cc",
     "host_change_notification_listener_unittest.cc",
     "host_config_unittest.cc",
+    "host_experiment_session_plugin_unittest.cc",
     "host_extension_session_manager_unittest.cc",
     "host_power_save_blocker_unittest.cc",
     "host_session_options_unittest.cc",

remoting/host/host_experiment_session_plugin.cc

@@ -0,0 +1,50 @@
+// Copyright 2016 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 "remoting/host/host_experiment_session_plugin.h"
+
+#include "remoting/base/constants.h"
+#include "remoting/host/host_attributes.h"
+
+namespace remoting {
+
+using buzz::QName;
+using buzz::XmlElement;
+
+std::unique_ptr<XmlElement> HostExperimentSessionPlugin::GetNextMessage() {
+  if (attributes_sent_) {
+    return nullptr;
+  }
+  attributes_sent_ = true;
+  std::unique_ptr<XmlElement> attributes(
+      new XmlElement(QName(kChromotingXmlNamespace, "host-attributes")));
+  attributes->SetBodyText(GetHostAttributes());
+  return attributes;
+}
+
+void HostExperimentSessionPlugin::OnIncomingMessage(
+    const XmlElement& attachments) {
+  if (configuration_received_) {
+    return;
+  }
+
+  const XmlElement* configuration = attachments.FirstNamed(
+      QName(kChromotingXmlNamespace, "host-configuration"));
+  if (!configuration) {
+    return;
+  }
+
+  configuration_received_ = true;
+  configuration_ = configuration->BodyText();
+}
+
+bool HostExperimentSessionPlugin::configuration_received() const {
+  return configuration_received_;
+}
+
+const std::string& HostExperimentSessionPlugin::configuration() const {
+  return configuration_;
+}
+
+}  // namespace remoting

remoting/host/host_experiment_session_plugin.h

@@ -0,0 +1,41 @@
+// Copyright 2016 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 REMOTING_HOST_HOST_EXPERIMENT_SESSION_PLUGIN_H_
+#define REMOTING_HOST_HOST_EXPERIMENT_SESSION_PLUGIN_H_
+
+#include <memory>
+#include <string>
+
+#include "remoting/protocol/session_plugin.h"
+#include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
+
+namespace remoting {
+
+// A SessionPlugin implementation to send host attributes to client, and
+// receives experiment settings.
+class HostExperimentSessionPlugin : public protocol::SessionPlugin {
+ public:
+  using SessionPlugin::SessionPlugin;
+
+  // protocol::SessionPlug implementation.
+  std::unique_ptr<buzz::XmlElement> GetNextMessage() override;
+
+  void OnIncomingMessage(const buzz::XmlElement& attachments) override;
+
+  // Whether we have received configuration from client.
+  bool configuration_received() const;
+
+  // The configuration sent from client, may be empty.
+  const std::string& configuration() const;
+
+ private:
+  bool attributes_sent_ = false;
+  bool configuration_received_ = false;
+  std::string configuration_;
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_HOST_HOST_EXPERIMENT_SESSION_PLUGIN_H_

remoting/host/host_experiment_session_plugin_unittest.cc

@@ -0,0 +1,64 @@
+// Copyright 2016 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 "remoting/host/host_experiment_session_plugin.h"
+
+#include <memory>
+
+#include "base/bind.h"
+#include "remoting/base/constants.h"
+#include "remoting/host/host_attributes.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/webrtc/libjingle/xmllite/xmlelement.h"
+
+using buzz::QName;
+using buzz::XmlElement;
+
+namespace remoting {
+
+TEST(HostExperimentSessionPluginTest, AttachAttributes) {
+  HostExperimentSessionPlugin plugin;
+  std::unique_ptr<XmlElement> attachments = plugin.GetNextMessage();
+  ASSERT_TRUE(attachments);
+  ASSERT_EQ(attachments->Name(),
+            QName(kChromotingXmlNamespace, "host-attributes"));
+  ASSERT_EQ(attachments->BodyText(), GetHostAttributes());
+
+  attachments.reset();
+  attachments = plugin.GetNextMessage();
+  ASSERT_FALSE(attachments);
+}
+
+TEST(HostExperimentSessionPluginTest, LoadConfiguration) {
+  std::unique_ptr<XmlElement> attachment(
+      new XmlElement(QName(kChromotingXmlNamespace, "attachments")));
+  XmlElement* configuration =
+      new XmlElement(QName(kChromotingXmlNamespace, "host-configuration"));
+  configuration->SetBodyText("This Is A Test Configuration");
+  attachment->AddElement(configuration);
+  HostExperimentSessionPlugin plugin;
+  plugin.OnIncomingMessage(*attachment);
+  ASSERT_TRUE(plugin.configuration_received());
+  ASSERT_EQ(plugin.configuration(), "This Is A Test Configuration");
+}
+
+TEST(HostExperimentSessionPluginTest, IgnoreSecondConfiguration) {
+  std::unique_ptr<XmlElement> attachment(
+      new XmlElement(QName(kChromotingXmlNamespace, "attachments")));
+  XmlElement* configuration =
+      new XmlElement(QName(kChromotingXmlNamespace, "host-configuration"));
+  attachment->AddElement(configuration);
+  configuration->SetBodyText("config1");
+  HostExperimentSessionPlugin plugin;
+  plugin.OnIncomingMessage(*attachment);
+  ASSERT_TRUE(plugin.configuration_received());
+  ASSERT_EQ(plugin.configuration(), "config1");
+
+  configuration->SetBodyText("config2");
+  plugin.OnIncomingMessage(*attachment);
+  ASSERT_TRUE(plugin.configuration_received());
+  ASSERT_EQ(plugin.configuration(), "config1");
+}
+
+}  // namespace remoting

remoting/protocol/session_plugin.h

@@ -7,9 +7,6 @@
 
 #include <memory>
 
-#include "base/callback.h"
-#include "remoting/protocol/jingle_messages.h"
-#include "remoting/protocol/session.h"
 #include "third_party/libjingle_xmpp/xmllite/xmlelement.h"
 
 namespace remoting {