Well, not solely for Android and Chrome - but presumably those products are the headliners affected by this patent bid. Google is currently bidding on a collection of over 6,000 patents held by Nortel Networks, which is selling the portfolio as part of bankruptcy proceedings. Google tossed its name in the hat with an initial offering of $900,000,000 - not exactly chump change.
Many of the patents relate to wireless technology (such as LTE) and data networking, but undoubtedly Google found some of them to be in the particular interest of protecting Android and Chrome, as Google's General Counsel indicted on the company's blog.
If successful, we hope this portfolio will not only create a disincentive for others to sue Google, but also help us, our partners and the open source community—which is integrally involved in projects like Android and Chrome—continue to innovate. In the absence of meaningful reform, we believe it's the best long-term solution for Google, our users and our partners.
Many large tech companies endlessly lobby for patent reform in the US (while simultaneously buying and filing a stream of patents every year) - in part because purchases like this are what have become the cost of doing business when you're a big litigation target like Microsoft, Apple, or Google. Essentially, the strategy here is to buy up (or file) as many apparently enforceable patents as possible, for use as a deterrent (and defense) against would-be patent claims and to keep them out of the hands of competitors.
This practice is seen by many as inherently backwards - as the primary purpose of a patent is to enforce an exclusive right to an idea, not to defend yourself against litigation. For big tech, however, amassing an arsenal of broadly enforceable patents has become essential to protecting products from potentially disastrous intellectual property lawsuits.
Reportedly, Apple and RIM are also interested parties in the Nortel portfolio bid, a factor which likely helped to cement Google's decision to make an offer.
Google is currently involved in a number of lawsuits regarding Android, most notably in a patent infringement action brought by Oracle. Whether any of the Nortel patents would help it in regard to that litigation is unknown.