Google has published the commit changes that came with the Android security updates that Google released today.
They aren't easy to read unless you're a developer, but each commit has been documented for all to see.
We already know about the Unicode 8.0 Emoji, T-Mobile support for Band 12 on the 5X and 6P, and the resurgence of the Until Next Alarm do not disturb option.
Another big change includes a performance increase for ART during app installation. In the comments they used the Nexus 9 as an example...