Revert "window: Check if we can use CSD before enabling them"

Revert "window: Check if we can use CSD before enabling them"

This reverts commit c5e5ee67490e7e7af56052d8f8beb75db002c2f1.

It turns out that this commit breaks the default sizing of GtkWindow,
which in turn causes the window to be smaller than the handle size,
which ends up sending invalid rectangles to Cairo.

We'll have to find another way to fix the CSD issue.

See also: https://bugzilla.gnome.org/show_bug.cgi?id=751140

https://bugzilla.gnome.org/show_bug.cgi?id=750343