While you can use browsers other than Safari on iOS, and have been able to for a few years now, none of those alternatives are allowed to bring their own rendering engines to Apple's platform. So they all have to use the built-in WebKit rendering engine that also powers Safari. This is why up until today the code for Google Chrome's iOS version has been kept separate from the Chromium open source project, which is available for developers to use to compile browsers for the other operating systems that Chrome runs on. Yet Google has "spent a lot of time over the past several years" making...
Source: http://www.gsmarena.com/google_chrome_for_ios_is_now_open_source_too-news-23096.php
