RootMarkingVisitor 2399 src/mark-compact.cc   RootMarkingVisitor root_visitor(heap());
RootMarkingVisitor   47 src/mark-compact.h class RootMarkingVisitor;
RootMarkingVisitor  638 src/mark-compact.h   friend class RootMarkingVisitor;
RootMarkingVisitor  682 src/mark-compact.h   void MarkRoots(RootMarkingVisitor* visitor);