Android section is untested

[mgeisler]

We need to figure out a way to test the code in the Android section. I'm teaching the class right now, and I've discovered several places where the code has drifted from AOSP in such a way that it no longer compiles.

[mgeisler]

While fixing this, I realized that we should change how we store the Android examples: if we could include them somewhere in AOSP, we would be forced to keep them current as the platform evolves.

We would then pull in the relevant pages and examples as part of a build process — or perhaps we could simply include them via a Git sub-module? I don't have a lot of experience with those, but since AOSP is a large collection of Git repositories, it seems reasonable to assume that we could pull in one of these repositories as a sub-module.