[Chromoting] Use HostExperimentSessionPlugin in host

remoting/protocol/protocol_mock_objects.cc

Index: remoting/protocol/protocol_mock_objects.cc
diff --git a/remoting/protocol/protocol_mock_objects.cc b/remoting/protocol/protocol_mock_objects.cc
index 70581e4b134a74824f7d5838113d0194964f09d7..39f2137605839a20c482aa467041e16289d7495b 100644
--- a/remoting/protocol/protocol_mock_objects.cc
+++ b/remoting/protocol/protocol_mock_objects.cc
@@ -51,6 +51,23 @@ MockSession::MockSession() {}
 
 MockSession::~MockSession() {}
 
+void MockSession::AddPlugin(SessionPlugin* plugin) {
+  DCHECK(plugin);
+  for (const auto& message : attachments_) {
+    if (message.attachments) {
+      plugin->OnIncomingMessage(*(message.attachments));
+    }
+  }
+}
+
+void MockSession::SetAttachment(size_t round,
+                                std::unique_ptr<buzz::XmlElement> attachment) {
+  while (attachments_.size() <= round) {
+    attachments_.emplace_back();
+  }
+  attachments_[round].AddAttachment(std::move(attachment));
+}
+
 MockSessionManager::MockSessionManager() {}
 
 MockSessionManager::~MockSessionManager() {}