Current frame is stored in a scene, and scene might have multiple view
layers. The inactive view layers were not informed about scene's frame
being changed, so when user switched back to view after changing scene
frame it was in an inconsistent state between current scene frame and
animation.

Now we tag scene for time changes, so dependency graph can catch up
and do proper update.

Currently tagging is from quite generic place. Probably better approach
would be to tag from where frame is actually being assigned. Downside
of this is that it's easy to miss some places.