WIP: Updated search-to-thread to current master.

The existing MR !4 for this feature is 11 months old and 189 commits behind master, so I updated it to match current master.

I also added a test, but the test is incomplete: it does not actually check whether search has scrolled down. This would involve adding Selenium to the build, which seemed a little heavy-weight for a feature like this. Suggestions on improving the code and test are appreciated!