bug#16630: desktop-auto-save seems confusing

[Glenn Morris]

Juri Linkov wrote:

> Yes, definitely `desktop-auto-save-set-timer' have to be called
> in every place that changes one of the preconditions of
> `desktop-auto-save' to save the desktop:

Why doesn't desktop-save-mode simply enable the auto-save timer?
The timer function itself seems to take the necessary steps to ensure it
only actually does something when appropriate.