src/Pure/PIDE/markup.scala

       }
   }
 
   object Command_Timing extends Properties_Function("command_timing")
   object Theory_Timing extends Properties_Function("theory_timing")
+  object Session_Timing extends Properties_Function("session_timing")
   object ML_Statistics extends Properties_Function("ML_statistics")
   object Task_Statistics extends Properties_Function("task_statistics")
 
   object Loading_Theory extends Name_Function("loading_theory")
   object Build_Session_Finished extends Function("build_session_finished")