Static analysis reveals "phase_process" local variable is unused here:

void ShenandoahTraversalGC::weak_refs_work_doit() {
  ...

  ShenandoahPhaseTimings::Phase phase_process = ShenandoahPhaseTimings::weakrefs_process;

Indeed, we are missing ShenandoahGCPhase scope, like ShenandoahConcurrentMark::weak_refs_work_doit() has. New Traversal-specific counter needs to be added, and used with ShenandoahGCPhase here.