Test case for:
   Bug 22441 -- Unexpected shift with push_group and pop_group
   https://bugs.freedesktop.org/show_bug.cgi?id=22441

This is a test that demonstrates the error in the pdf backend when using
groups on surfaces with non-integer sizes. In order to create such a
surface, we need to update the boilerplate to use doubles instead of
integers when specifying the surface size.