In G1HeapSizingPolicy::full_collection_resize_amount there is some comment and code related to handling when this method is called in the remark pause.

It is not called in the remark pause any more since JDK-8248324, so this vestigial code should be removed as well.

  const size_t used_after_gc = capacity_after_gc + allocation_bytes -
                               _g1h->unused_committed_regions_in_bytes() -
                               // Discount space used by current Eden to establish a
                               // situation during Remark similar to at the end of full
                               // GC where eden is empty. During Remark there can be an
                               // arbitrary number of eden regions which would skew the
                               // results.
                               _g1h->eden_regions_count() * G1HeapRegion::GrainBytes;