Updates the scroll frame's scroll child rectangle.
- You were required to call this when you changed the contents of your ScrollFrame prior to patch 2.3. You no longer need to call it now. If a child frame, texture or fontstring has changed, the scroll parent will automatically recalculate it's scroll rect and dispatch events appropriately.
- You do need to call it before calling your own
:SetVerticalScroll()to flush pending updates (for instance after you inserted text in the scrolling edit box)