Currently, tile tasks are ordered based on heuristics which attempt to put the highest priority tasks first.

The ordering is usually correct. However, we can occasionally hit a case where a tile in the soon bucket which is *not* needed for activation is prioritized higher than a tile in the soon bucket that *is* needed for activation.

This may happen if the tile is in the pending visible rect for the active tree, but not in the pending tree.

We should investigate and fix this ordering.