When encountering inline SVG and MathML content in an HTML document, there are certain "integration points" which transition back into the HTML parsing ruleset. Previously, the HTML API was incorrectly switching into the namespace of the element transitioning into that ruleset.
In this patch, the correct transition is made, where all integration points refer to HTML rules, while non-integration points refer to the rules of the namespace corresponding to the token itself.
Developed in https://github.com/wordpress/wordpress-develop/pull/7425
Discussed in https://core.trac.wordpress.org/ticket/61576
Props dmsnell, jonsurrell.
See #61576.
Built from https://develop.svn.wordpress.org/trunk@59099
git-svn-id: http://core.svn.wordpress.org/trunk@58495 1a063a9b-81f0-0310-95a4-ce76da25c4cd
ed654177cd