Google I/O 2012 时就已经宣布对 android2.3+ 的 Google Play 实行增量升级（Smart app updates）

Smart app updates : For Android 2.3, Gingerbread devices and up , when
there is a new version of an app in Google Play, only the parts of the
app that changed are downloaded to users’ devices. On average, a smart
app update is a third the size of a full apk update. This means your
users save bandwidth and battery and the best part? You don’t have to
do a thing. This is automatically enabled for all apps downloaded from
Google Play. 1

实现来说是通过 bsdiff 来进行差分，详细的分析可以参见 这篇 blog .