(1) LO as a browser plugin, displaying LO documents directly in a browser window (enabled via LO's "Tools - Options... - Internet - Browser Plug-in"). (configure.ac uses the term ENABLE_NPAPI_INTO_BROWSER for this.)
(2) Plugging browser plugins into LO. One known use-case was (is?) to display .swf content via the Adobe flash player plugin, at least on Mac OS X and Windows. This feature was previously discussed in the mail thread starting at <http://lists.freedesktop.org/archives/libreoffice/2012-November/041259.html> "LO as an NPAPI browser plugin host?," and retained in particular for <http://lists.freedesktop.org/archives/libreoffice/2012-November/041439.html>. (configure.ac uses the term ENABLE_NPAPI_FROM_BROWSER for this.)
There is long-standing issue <https://bugs.freedesktop.org/show_bug.cgi?id=45071> "Browser plugin option not working" that claims that feature (1) is not working in certain (Windows) scenarios (while it is known to work in certain Linux scenarios at least).
Some comments in that issue suggest to remove feature (1), and there is now patch <https://gerrit.libreoffice.org/#/c/9644/> "Partial fix for bug 45071 - Remove NPAPI support" attempting to remove both features (1) and (2).
What is our rough consensus on these features?For (1), is it a feature worthy enough to keep---at least in the known-good scenarios, potentially removing it from the known-bad ones or even investing into fixing it there?
For (2), is the evaluation from late 2012 still relevant? I at least see no pressing need to tie the fate of feature (2) to that of feature (1), but overall code reduction of course isn't bad, either.
Stephan