xDeltaTime (in xChrono) is use here and there to obtain somme monitoring assesment on code performance. Thus it should not be anylonger in Xfem. It's natural place is in eXlibriss_tools. For example in solverinterface test some test do not need any xfem suff but are linking to this library just because xDeltaTime is locate there.
xChrono.h/cc to migrate in eXlibriss_tools with namespace change.