When we try to update the FB, we might face the case in which the effect target
framebuffer does not need any redraw, because it's already properly sized and
scaled, but the filter applied to the pipeline is not, because it has been
computed for a non-fractional scaling.

This is happens for example to clutter actors with a flattening effect (i.e.
override redirect mode set), that might have been generated properly for a
celied scaling level, but when we go fractional we need to ensure to use a
linear filter, as the 1:1 texel:pixel assumption is not true anymore.

https://bugzilla.gnome.org/show_bug.cgi?id=765011