Use Case: Sometimes a user will press the "Back" button unintentionally, and that will reset his playing track position.
If a track was played on Desktop Soundcloud the time should be saved, so if the user comes back to the Soundcloud page the user will be able to resume playing from the same position.
That imho will improve the UX of the desktop player.
It's already implemented in the BBC Radio 1 Website Player , for reference. (http://www.bbc.co.uk/programmes/b006ww0v)