edit: Now even better! It adds a context menu to right-click a track or artist and search Spotify right then and there. EXCELLENT idea, and I will use this daily.

Works great! Looks great! I tried a few extensions that are supposed to do what this does, but this is hands down the best.
The only legitimate criticism I have is that there's no volume control or time scrubber, but honestly I need those so infrequently that it's not a major inconvenience. Also, I dunno if it's possible to tie it to a keyboard's media controls, but that'd be sweet.