Confirmed this earlier today after chatting with some people. This is really bad.

Here's what we're pretty sure is happening (need to confirm that):

• Cirrus is parsing the JS page even though it shouldn't.
• Since it's being treated as wikitext and being parsed, we're getting weird results when we hit a header tag in Javascript (in this case, no parseable closing tag)
• We generate bogus sections as a result that shouldn't go anywhere

We should (in no particular order):

• Check content handling to make sure CSS/JS pages aren't getting parsed like wikitext
• Make sure core Special:Search is not being insane when given obviously bogus sections. See also bug 59717 where lsearchd is giving us bogus section titles as well

There's a second bug (but might just be a symptom of this bug) in that we see two distinct titles (vector.js and Tools.js) but they've got the same section name (which only exists in the former).

Change 115214 had a related patch set uploaded by Chad:
Don't use parsed wikitext when dealing with CSS/JS pages

https://gerrit.wikimedia.org/r/115214

Change 115214 merged by jenkins-bot:
Don't use parsed wikitext when dealing with CSS/JS

https://gerrit.wikimedia.org/r/115214

Will go out with next deploy cycle and results will still be wonky until indexes are rebuilt.