Demo: https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=13622

a is an unknown MathML element (currently), and is not rendered correctly in Gecko. The spec says unknown elements should be treated as mrow.

Unknown MathML elements behave the same as the mrow element.

https://w3c.github.io/mathml-core/#ref-for-dfn-unknown-mathml-element-2

In https://github.com/w3c/mathml-core/issues/142 there's a proposal to make a the MathML "link" element.

FWIW it seems there are some failures, mostly about tables: https://treeherder.mozilla.org/jobs?repo=try&revision=870c0a2dec9f8d240d5eafab1887219fc11915df

Also some passes. I don't have time to finish this up at this very moment.

Extends https://phabricator.services.mozilla.com/D244634.

Added mtable, mtr, mlabeledtr and mtd as exceptions.

Co-authored-by: Emilio Cobos Álvarez <[email protected]>

https://hg.mozilla.org/mozilla-central/rev/ca8c819dba01