In child class of `RefProcTask`, `void rp_work(...)` starts with `ResourceMark`, which is used to guard against memory leak. However, in that context, it's not obvious what resource it's protecting at first glance.

Better move the marker closer to where it's needed for improved precision and readability.

---------------------------- Update ---------------------

During the review, it's suggested to remove those trace-msg completely, because the signal-to-noise ratio is too low.