When an app reaches 1 billion installs on the Play Store, it's like being officially recognized as one of the cool kids. Chrome for Android is the latest to join the clique, sliding through the door just a week behind Hangouts, making it the 12th app to flash a 10-digit install base.
While induction into this elite group hasn't been quite as impressive since membership hit the double digits, Chrome is among the first of Google's apps that doesn't owe all of its success to pre-installs. The first beta release of Chrome came in early 2012 and only supported Android 4.0 Ice Cream Sandwich. At this time, ICS was still new and only a handful of devices were shipping with it. There were still brand new phones launching with Gingerbread.
It wasn't until several months later that Chrome would come pre-installed for the first time on the original Nexus 7 running Android 4.1 Jelly Bean. Most manufacturers continued to stick exclusively to their own "stock" browsers until 2013, when many of them started to include both browsers. These days, Chrome is a standard part of the package for any Google partner, but that doesn't diminish the sheer number of people that chose to seek it out in the beginning.
The reach of this single browser is hardly limited to the Play Store. Analytics agencies and marketing firms can't seem to agree on when it happened, but everybody acknowledges Chrome has taken the lead in browser market share from Internet Explorer. It has also seen significant traction on iOS in the Apple App Store. (Just imagine if Apple shared install numbers.) And with the release of Kit Kat, the underlying components that drive the rendering and scripting capabilities are now fundamental parts of Android.
So, which app is going to be lucky number 13? Based on the current view from Android Rank, we can probably expect it to be either Street View or Play Music. There are a half-dozen Google apps sitting below the line, but it's certainly possible Samsung's Push Service, Skype, or Instagram (another Facebook property) could push their way over the edge at any time.