Account for CSS zoom in SVGPathElement::GetAsSimplePath.
This fixes most of the rendering in the blocked bug. The other issue is
transforms, which ideally would be auto-magically fixed by bug 878346...
Differential Revision: https://phabricator.services.mozilla.com/D215742
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1906270
gecko-commit: 7d25625355c04b27639a53ca219aeff6b8030251
gecko-reviewers: longsonr