P4
In `check_obj_during_refinement`:
```
assert(g1h->is_in_reserved(obj), ... // <- this can be strenghen to `is_in`
HeapRegion* from = g1h->heap_region_containing(p);
assert(from->is_in_reserved(p) || (from->is_humongous() ... // <- this can be replaced by `is_in`
```
```
assert(g1h->is_in_reserved(obj), ... // <- this can be strenghen to `is_in`
HeapRegion* from = g1h->heap_region_containing(p);
assert(from->is_in_reserved(p) || (from->is_humongous() ... // <- this can be replaced by `is_in`
```
