The previous implementation was using an ad-hoc regular expression which
was matching inside the data-mw attribute of Parsoid output, eg:
<sup about="#mwt42" [...] typeof="mw:Extension/ref mw:Error" data-mw="{"name":"ref","attrs":{"name":"infobox_stats_ref_rail"},"body":{"html":"<style data-mw-deduplicate=\"TemplateStyles:r1133582631\" typeof=\"...">
After substitution, the <link> element inserted contained " instead of
" and so broke out of the attribute.
Instead use a proper HTML tokenizer (via wikimedia/remex-html) so that
we don't allow bogus matches inside attribute values.
To fix up tests:
* Don't deduplicate styles when parsing UX messages (also helps performance)
* Don't deduplicate styles in ContentHandler integration tests
* Don't deduplicate styles by default in parser tests
(unless explicit option is set)
Depends-On: Id9801a9ff540bd818a32bc6fa35c48a9cff12d3a
Depends-On: I5111f1fdb7140948b82113adbc774af286174ab3
Followup-To: Ic0b17e361bf6eb0e71c498abc17f5f67f82318f8
Change-Id: I32d3d1772243c3819e1e1486351d16871b6e21c4
82da9cf14b