It seems as though Samsung is now in the practice of building their own browser engine, and they've teamed with Mozilla to do so. Mozilla is planning to implement its new Servo browser engine, which is reported to take advantage of the ARM architecture.
Opera to switch to using WebKit for its Android browser
Opera's new software is a WebKit-based browser designed with touchscreen devices in mind. The browser is supposed to be Opera’s answer to Chrome and Safari, the two major browsers that use the WebKit engine.