When Chrome launched, it leap frogged its competitors by walling away each tab into its own processor. This yield greater stability as a poorly coded or malicious web site couldn’t directly crash the browser. Microsoft released some highly speculative research that indicated Internet Explorer might some day follow suit. Mozilla started working on Electrolysis to do something similar and even recently released a nightly build bearing some of the earliest fruit of that effort.
Now the WebKit project, driven primarily by Apple but used by many other projects, has hopped on the multiple process bandwagon. Clint Ecker at Ars Technica has the details which read very nicely for programmers embedding the cutting edge web rendering toolkit. Even though the news comes from a mailing list announcement, there seems to be some code somewhere as Ecker refers to three out of fours methods as being already implemented for client programmers to listen in on separate browser processes. There is a great deal more detail on the project page for WebKit2.
I hope this added weight accelerates the trend behind a design that should yield much more robust browsers in the face of ever increasing complexity in modern and highly demanding web applications.