UnmarkRecursively 6634 src/heap.cc            tracer_->UnmarkRecursively(p, this);
UnmarkRecursively 6671 src/heap.cc      UnmarkRecursively(root, &unmark_visitor);
UnmarkRecursively 6751 src/heap.cc      UnmarkRecursively(reinterpret_cast<Object**>(&map_p), unmark_visitor);
UnmarkRecursively 2715 src/heap.h       void UnmarkRecursively(Object** p, UnmarkVisitor* unmark_visitor);