Stephen Shankland/CNET

Mike Shaver already announced last year he was moving to Facebook after resigning as vice president of technical strategy for Firefox.

And now we know what he'll be doing there: engineering manager for Android app development.

Given the immense membership of Facebook, there are few mobile apps in the world that are as important as Facebook's. The company announced in December that Facebook has 800 million users.

Shaver tweeted on Friday, "This week I started as the eng mgr for Facebook's Android team. Doing cool stuff -- some probably obvious, some rather not. And hiring!"

The news caught the attention of some tech insiders. Mike Belshe of start-up Twist offered congratulations and an suggestion that Facebook should use SPDY, a Web-acceleration technology he developed while at Google; SPDY now is being built into Firefox. "I figured we'd get it for free from Android's WebView and HTTP libraries :-P," Shaver replied, a little dig at the fact that Android's browser doesn't yet support SPDY.

The new job means Shaver is changing from one hot market--browser development and its closely related field of Web development--for another. With the explosive growth of smartphones, mobile apps today are ever more important as a mechanism for using the Internet.

The two fields aren't as far apart as it might appear, though.

When Firefox evangelist Asa Dotzler asked Shaver, "Will you all re-write the Android Facebook app as a Web app?" Shaver replied that the app already is "mostly a wrapper around the m [mobile] site," but that Facebook needs more interfaces that browsers don't yet offer to software. Specifically, Shaver said, the Facebook app needs interfaces to send notifications, to manage a mobile device's camera, and to interact with its contact list.

Shaver, a Canadian, had thought it possible he could start working at Facebook in November, but cautioned at the time that exact timing was up to the United States' Immigration and Naturalization Service. It appears Facebook and Shaver had to wait a few more weeks than they would have preferred.

Updated 6:05 a.m. PT to correct name of Mike Belshe's current employer to Twist.