In May, Google said it was extending Firebase — a cloud-based mobile software tool it acquired in 2014 — into a broader developer platform, competing with similar offerings from Facebook Inc. and Twitter's Fabric. Firebase gives mobile app creators tools to build and monitor their apps more easily. It's a critical service for Google's effort to lure developers away from from Apple Inc., a more lucrative ground, and push them to create apps for the mobile web, where Google makes a bulk of its advertising dollars.