I'm still learning how to upload patches correctly using arc, apologies that the first commit is unrelated.
Problem
Currently, it's difficult to use the NLA system for users who are only interested in using it as animation layers. (1) Entering tweak mode hides strips which are not evaluated. If the user wanted to edit a different strip, they must exit tweak mode, look for the strip, then re-enter tweak mode. (2) This should've been a separate diff but syncing strip length to the action length changes the overall NLA evaluation result. This is due to only the length being synced instead of the start and end times.
Solution
1) All strips are always shown. The user can now see the next strip they want to start editting. While in tweak mode, if the user selects a new strip, we remain in tweak mode. The process is now simplified to: User wants to edit a different strip so all they have to do is select it.
2) Both strip start and end sync to the action, accounting for strip speed scaling. Now when the user exits tweak mode, the overall NLA result is unchanged.
Old: Changing tweaked strip
{F8495351}
New: Changing tweaked strip
{F8495353}
Old: Sync Strip Length which changes the NLA result
{F8495355}
New: Sync Strip Length which preserves the NLA result
{F8495356}
revert unrelated changes