[Chromoting] Implement HostExperimentSessionPlugin

remoting/protocol/BUILD.gn

Index: remoting/protocol/BUILD.gn
diff --git a/remoting/protocol/BUILD.gn b/remoting/protocol/BUILD.gn
index c2464af15a94f4fa33832a77c61b99b9d0bfb7e6..f11d3b9704b39aa3eea462678e18506bf84c0543 100644
--- a/remoting/protocol/BUILD.gn
+++ b/remoting/protocol/BUILD.gn
@@ -61,6 +61,8 @@ static_library("protocol") {
     "host_control_dispatcher.h",
     "host_event_dispatcher.cc",
     "host_event_dispatcher.h",
+    "host_experiment_session_plugin.cc",
+    "host_experiment_session_plugin.h",
     "host_stub.h",
     "host_video_dispatcher.cc",
     "host_video_dispatcher.h",
@@ -146,6 +148,8 @@ static_library("protocol") {
     "session_config.cc",
     "session_config.h",
     "session_manager.h",
+    "session_plugin.cc",
+    "session_plugin.h",
     "socket_util.cc",
     "socket_util.h",
     "spake2_authenticator.cc",
@@ -306,6 +310,7 @@ source_set("unit_tests") {
     "connection_tester.h",
     "connection_unittest.cc",
     "content_description_unittest.cc",
+    "host_experiment_session_plugin_unittest.cc",
     "http_ice_config_request_unittest.cc",
     "ice_transport_unittest.cc",
     "input_event_tracker_unittest.cc",