The patch is updating efl_ui_grid overal functionality including row/column count feature
and relative size feature which calls partition.
The partition is grid specific feature which works similar like our size hint weight.
if user set the partition [N * M], get the item size by calculating N and M numbers item to
be shown in the viewport.
this value is depending on the viewport size, so if viewport is resized,
item size will be resized by viewport changes and partition will not be changed.
item_size_set is for absolute size on the other hand, regardless of viewport changes,
it still show the same size of item.
both value can be set in indivisual axis, but the final call will be always respected.
see more details in the documents in efl_ui_grid.eo.