Google could agree to indemnify app developers for legal fees. There are certain restrictions on other people paying for your legal defense but it's commonly done subject to those restrictions.
They could also take the first app developer to get sued under the patent and pay for them to file a CBM review. Or file an IPR or PGR in their own right seeking to invalidate the patent.
If Google just paid for the defense of the developers, without patent reform, wouldn't that just encourage more patent trolls to arise, knowing there is a massive pot of gold?
Only if the trolls won. On the other hand, if Google's lawyers gave them the smack down then all the patent trolls would go scurrying back under the rocks they crawled out from
Even when trolls lose, they're typically shell companies with no assets, so they can't pay for the legal fees of the winner (they just go bankrupt) and the winner still loses in terms of money.
Spin off a shell corp for each individual patent that is litigated, if a loss ever occurs, the only thing "on the line" in a bankruptcy is the single patent that presumably just lost.
Or Google can sue patent troll for false claims that they own patent on Google Play Store and seek compensation for their financial damages caused by those false claims.
In this case "financial damages" may be interpreted as thousands of developers that presumably did not get involved with Google Play platform because of these false claims.
Plus Google can claim litigation costs.
Also clearly there is a damage to reputation of the Google, since we are discussing here that they need to get involved in this case. I am not sure if they can get compensated for that as well.