https://lists.w3.org/Archives/Public/www-style/2015Apr/0094.html We should parse perspective-origin as a <position>, which includes the edge-relative syntax like "right 3em bottom 10px"
Note that the old 3 value syntax should be rejected. https://wpt.fyi/results/css/css-transforms/parsing/perspective-origin-parsing-invalid.html Discussed in https://github.com/w3c/csswg-drafts/issues/2140
Fix via bug 189142. *** This bug has been marked as a duplicate of bug 189142 ***