Add a test for an initial negative scaling transform that requires an isolated layer
With !899 (merged), I'm a bit anxious that the test suite doesn't have a case for having an initial cr
with a negative scaling transform (e.g. cr.scale(-1.0, -1.0)
, that also has an SVG with an isolated layer. Before !899 (merged), that would cause DrawingCtx::size_for_temporary_surface
to return a negative size; after it, I'm not sure that the temporary surface has the correct transform.