This commit ports over the last remaining operation for tiling that doesn't work
on the paint thread.
The difficult part for edge padding is that it is done outside of ValidateTile
so it doesn't have an associated CapturedTilePaintState to be added to as an
operation. We need it to be in the same paint state so that it's guaranteed
to be run after painting has finished.
This commit changes edge padding to instead be decided inside of ValidateTile
and either sent to the paint thread if there is OMTP or executed right away.
MozReview-Commit-ID: JDD4rH1fVwW
--HG--
extra : source : 9b0a54842d3169960a606fa1dd335acf6aa70dbe
extra : intermediate-source : bcbab66c16c5cc2b917f12b4481bbbb8fe3eb097
Ryan Hunt