surface-actor: Remove unused APIs
window-actor: Rebuild the shape and mask when the surface updates

Connecting to size-changed is wrong -- size-changed tells us when
we *told* the X server or resize the window. For X11, we're sort of
guaranteed that the surface will be updated at some point before the
next frame, but for Xwayland, we can't be sure that the new surface is
attached at this point.

This fixes weird artifacts when resizing apps like xclock.
shadow-factory: Untabify
shadow-factory: Fix style