Function capital_P_dangit is applied directly to document title

[dragunoff]

This formatting function is normally applied via filters. But in wp_get_document_title it's called directly and thus its effect is forced onto the user. It should instead be hooked to the filter document_title_parts.

[jeremyfelt]

It does seem odd that wptexturize(), convert_chars(), and capital_P_dangit() are all run on the title after the document_title_parts filter is applied in wp_document_title().

I'm not sure if we can adjust the order now that it's been there for a few years, but it looks like there's room for a document_title filter that is applied before wp_document_title() returns $title. We can then use the familiar pattern (default-filters.php) to apply each of those in a way that can be unhooked.

Because wp_document_title() is expected to return a string safe for use in <title></title>, esc_html() should probably be run after the document_title filter is applied.