899139bc_for_Tracing_in_SQL_Server_2014__Description
[Package name] sqlserver [Event name] query_optimizer_force_both_cardinality_estimation_behaviors [Description] 
Both traceflags 2312 and 9481 were enabled, attempting to force both old and new cardinality estimation behaviors at the same time. The traceflags were ignored. Disable one or both of the traceflags.
New Extended Events for Tracing in SQL Server 2014
Description