[Chromoting] Use HostExperimentSessionPlugin in host

remoting/protocol/fake_session.cc

Index: remoting/protocol/fake_session.cc
diff --git a/remoting/protocol/fake_session.cc b/remoting/protocol/fake_session.cc
index 56cbd51b1e5390eaa074aae26744b188fe1d3b43..6f0c8b8072516916e6d659605faa17645df0c8d9 100644
--- a/remoting/protocol/fake_session.cc
+++ b/remoting/protocol/fake_session.cc
@@ -104,9 +104,21 @@ void FakeSession::ProcessTransportInfo(
   transport_->ProcessTransportInfo(transport_info.get());
 }
 
-// TODO(zijiehe): Supports SessionPlugin in FakeSession.
 void FakeSession::AddPlugin(SessionPlugin* plugin) {
-  NOTIMPLEMENTED();
+  DCHECK(plugin);
+  for (const auto& message : attachments_) {
+    if (message.attachments) {
+      plugin->OnIncomingMessage(*(message.attachments));
+    }
+  }
+}
+
+void FakeSession::SetAttachment(size_t round,
+                                std::unique_ptr<buzz::XmlElement> attachment) {
+  while (attachments_.size() <= round) {
+    attachments_.emplace_back();
+  }
+  attachments_[round].AddAttachment(std::move(attachment));
 }
 
 }  // namespace protocol