It should be easy to work with a Track that starts at non-zero time.

[jminor]

Currently, working with a Track that has a non-zero time involves using either a Gap, or a source_range with a negative start_time, or both. This is kind of awkward. This is a common scenario and should be simpler and more intuitive.

[meshula]

@jminor Do you still think this is an issue? I think we might be used to the current state of things by now :)