When `next_token()` was introduced, it introduced a regression in the HTML
Processor whereby void tags remain on the stack of open elements when they
shouldn't. This led to invalid values returned from `get_breadcrumbs()`.
The reason was that calling `next_token()` works through a different code path
than the HTML Processor runs everything else. To solve this, its sub-classed
`next_token()` called `step( self::REPROCESS_CURRENT_TOKEN )` so that the proper
HTML accounting takes place.
Unfortunately that same reprocessing code path skipped the step whereby void
and self-closing elements are popped from the stack of open elements.
In this patch, that step is run with a third mode for `step()`, which is the
new `self::PROCESS_CURRENT_TOKEN`. This mode acts as if `self::PROCESS_NEXT_NODE`
were called, except it doesn't advance the parser.
Developed in https://github.com/WordPress/wordpress-develop/pull/5975
Discussed in https://core.trac.wordpress.org/ticket/60382
Follow-up to [57348]
Props dmsnell, jonsurrell
Fixes#60382
Built from https://develop.svn.wordpress.org/trunk@57507
git-svn-id: http://core.svn.wordpress.org/trunk@57008 1a063a9b-81f0-0310-95a4-ce76da25c4cd
0dc136bcb9