For iOS 8, adds JavaScript Nitro to WebKit

As of iOS 8, however, it seems that decision has been reversed. All apps will now be able to use the same improved JavaScript engine that powers Safari. That means Google’s Chrome browser on iOS will now be just as quick as Safari, as will the pop-up browsers embedded in apps like Twitter and Facebook.

Mike Beasley | 9to5Mac

That's right developers, full access to the JavaScript Nitro engine (in addition to some of Safari's gesture based controls, and Safari's “supersmooth 60-frames-per-second scrolling using hardware acceleration and CoreAnimation”).