In the struggle to seize ground in the slowly developing mobile-wallet field, Google is expanding the functionality of its offering by adding easy, three-tap checkouts for e-commerce sites that provide Google Wallet as an option. The feature is designed to make Google Wallet a more attractive choice for consumers. But it should also help online retailers consummate m-commerce sales, 97% of which are abandoned on smartphones due to the difficulty of filling out payment information on a tiny screen.