The whole process took about 3 months, from the original conversation with the recruiter. I got a call from the recruiter and had a phone screen. After the phone screen, I heard back the next day, inviting me to come onsite to Mountain View. However, it took about 2 weeks to just schedule the on-site, which was then about 2 weeks off. In Mountain View, I interviewed with 4 people, and one for lunch. After the on-site interview, I sent thank you letters, but did not hear anything back for weeks. Then I followed up with a phone call, and again, and learned that the recruiter has not yet received feedback from people I interviewed with (this is now weeks past). When I followed up again, they said still no review, but they'd like to ask me to come out to Mountain View the second time, so that, as the recruiter has put it, she can get the required number of interviews in. This made me curious as to the whole review process. The candidate takes the time to prepare for the interview, fly to a different city, do their best, and the reviewer does not bother to submit their feedback (and is not pushed by Google to do so). Strange.
Second round on campus was with 2 people. After that, heard back in 2 weeks. All in all took 3 months.