I couldn't bear looking at how bloated C++ implementation is, so I implemented it in C++11 based on boost.fiber library: https://gist.github.com/4015306. Now it looks very similar to Go language code.
But I have to admit that Android's concurrency framework is more about message passing and actors than about fibers or coroutines. The fiber implementation is much more readable here.
Cool, looks much better :-). Normally, I really like Android's concurrency abstractions, but not for this one :-).