Fix handling of time in activity debug controls.
Fix handling of time in activity debug controls.

In activities, time is handled via the TimePassing event constructor.
But debug controls weren't taking effect on these events.  The speed
slider didn't change the speeds, and the step button didn't deliver
it.  This is now fixed.

google/codeworld,google/codeworld,pranjaltale16/codeworld,pranjaltale16/codeworld,alphalambda/codeworld,alphalambda/codeworld,alphalambda/codeworld,google/codeworld,pranjaltale16/codeworld