timeline: Use parent ids in order with its sub-surface id

wesgr expects that the ids are in order which doesn't happen with sub-surfaces. Most likely this was introduced a while back when the logging and timeline subscription was changed to allow working as a debug scope.

This adds a minor comment about that and a swaps the ids between the sub-surface and the parent id when we detect they are out of order. New sub-surfaces are still referring the correct parent ids.

Signed-off-by: Marius Vlad marius.vlad@collabora.com