[Chromoting] Add SessionPlugin in JingleSession

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 8782368cb53486c1983ab21c68fefb92b7f30599..5b0e62492dcadaa32e4c58d12438da25e177a03d 100644
--- a/remoting/protocol/protocol_mock_objects.cc
+++ b/remoting/protocol/protocol_mock_objects.cc
@@ -4,10 +4,12 @@
 
 #include "remoting/protocol/protocol_mock_objects.h"
 
+#include <memory>
 #include <utility>
 
 #include "base/logging.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "remoting/protocol/session_plugin.h"
 #include "remoting/protocol/video_stream.h"
 
 namespace remoting {
@@ -49,6 +51,8 @@ MockSession::MockSession() {}
 
 MockSession::~MockSession() {}
 
+void MockSession::Attach(std::unique_ptr<SessionPlugin> plugin) {}
+
 MockSessionManager::MockSessionManager() {}
 
 MockSessionManager::~MockSessionManager() {}