Tweak preview tabs timeout

[bbondy]

1. It should delay a bit more when moving from 1 tab to the other so there is no active tab in between.
2. Play with the hover time to avoid accidental previews but also don't make it too long.
3. The time it takes to reset to the "you need to hover" seems a bit too long

[bridiver]

I'm thinking maybe 150-200ms on activate/deactivate. Long enough to prevent accidental activation when moving the mouse around, but short enough to not really be very noticeable or require an "activation window" with no delay. I guess the activation window should exist, but it should only be about 250-300ms to prevent adding the activate and deactivate times together

[bbondy]

@BrendanEich suggest doing this based on pointer velocity instead of just timeout. I think that's a great idea.

[luixxiul]

+1 from support