Earlier quoted context omitted.
You can't compare Google Research against Mozilla Research. Google is really moving computer science forward, just look at their papers and real implementations (disclaimer: I am not a Google fan). If you compare the Google Chrome source code vs Firefox you will quickly understand how miles ahead Google is.
To be fair though Chrome was started from scratch in 2007/2008 whereas Firefox has a lot of legacy stuff still hanging around from the early 2000s.
WebKit forked KHTML in 2005.
KHTML actually started in late '98 if memory serves, when we rebooted Mozilla around Gecko.
/be