I have only experience with Chrome codebase and while it's C++ (which I don't personally like) it's pretty solid and most of the weird hairy stuff were the external linked libraries. But I didn't poke around THAT much.
That's certainly interesting but to give context for those not following the link: This is for entering into the address/search bar, so it covers all the work of searching history, performing network requests to autocomplete search terms, and displaying those results. It's not like entering a character into a regular text box on a page.
