PreserveTree

Attempt to delete the activity in-place without changing the start times of any activities anchored to it.

Consider the anchor chain A <- B <- C, where A starts at an absolute time and B and C are anchored.

• If A is deleted with PreserveTree, B will be set to start at the absolute time A.startTime + B.offset. C will be unchanged.

• If B is deleted with PreserveTree, C will be anchored to A with a new offset equal to B.offset + C.offset.

If an activity is anchored to the end of the deleted activity, the delete activity's duration is assumed to be 0, which may change the ultimate start time of the anchored activity.