In what is being seen as a potential challenge to Amazon but perhaps a conflict for retailers, Google plans to begin testing "buy buttons" in coming weeks. The Wall Street Journal reported last week that buttons will appear beside paid search results on mobile in the "Shop on Google" section. Clicking a button takes the shopper to another Google product page, where orders can be customized (sizes, colors, etc.) and shipping options explored before completing the purchase. Google will also store credit card information to let the shopper repeat the process again at another time. The goods...