It means that Google is experimenting with using Rust to build parts of Android. That could mean parts of the OS, tests, tools, SDK, etc...
As a simple example of why this isn't necessarily super interesting is Python has been in the Android tree for ages, but just for some build & test stuff.
But maybe it's interesting just in that the Google engineers working on Android have started playing with Rust enough to bother checking it in to the tree.
Pretty much what Mozilla did when Rust got more serious.
The second Android developer needing to use Rust will presumably have an easier time of it, but how much Android will really use it is speculative.
For Android you write JNI bindings with something like rust-jni.
So yes, you have to write bindings twice. For an example project check out https://github.com/dbrgn/candidateparser and https://www.reddit.com/r/rust/comments/7aam04/meetup_slides_...
But it's not something ordinary Android developers need to pay attention to.
</grumpy> I'm going to get some more coffee.
edit: this just means that Android developers can now include Rust-language components in Android itself.
Unsure about mingw/go, but they are likely deps for some Android ecosystem project.
2. Fuchsia seemingly supports Android apps (https://9to5google.com/2019/01/02/android-runtime-app-suppor...).
3. For 1 + 2, Android may need to include and compile a part of Fuchsia for interop.
My guess is that this addition is mostly for supporting Fuchsia, rather than using Rust directly in Android.
I wonder if Google is adding support, because it's also considering replacing the OpenSSL-forked BoringSSL with the Rustls crypto library:
That would be pretty cool, although I wonder if they shouldn't opt for a Noise Rust library instead: