In an effort to gain firmer control over the quality of Android smartphones, Google announced this morning that it has agreed to purchase Motorola Mobility for $12.5 billion. Google would also gain a nice fat portfolio of technology patents in the deal. Less talked about but perhaps just as important: the acquisition would make Google the largest set-top box supplier in the world (Remember Google TV? It’s still around). We say “would” because the deal isn’t done yet–antitrust regulators are going to have something to say about all this.