Boundary calculation when clipping is enabled ignores parent boundaries

[wouterlucas]

Issue:
When displaying a large grid of blocks an individual cell enables clipping for excess text
Individual cells boundaries are based off of the clipping area and ignore parent boundary status.

This causes the grid with cells to load all clipping enabled cells to load textures, ignoring boundaries.

With the test page:

Expected texture usage:

Current result:

All textures of the cells are loaded, even though the majority of the cells are not within the visible area.