Google has open sourced its Chrome for iOS code. The Chromium project has been providing developers with access to browser code that can be tested and modified, though it wasn't until now that Google for iOS' code was included.
The mobile browser hadn't been included as a result of iOS' requirement that browsers be built on top of WebKit. This meant Google had to support WebKit along with Blink, its rendering engine for other platforms.
It's possible new third-party iOS browsers could come out of the code's availability. You can view the code here.