Nope. If Google being sued by someone else with a similar business, having patents of their own might help with a countersuit -- Google would allege that Plaint

Nope. If Google being sued by someone else with a similar business, having patents of their own might help with a countersuit -- Google would allege that PlaintiffX was infringing Google's patents in the course of its own business. But a pure patent troll doesn't operate any business at all (other than collecting license fees), so they can't infringe somebody else's patents in the course of doing the nothing that they do.