I think a lot of the reason why I don't use Gentoo anymore is because the time I have to waste when I have to compile Chrome from scratch and wait two hours vs. just installing a precompiled .deb archive. :)
There is no source version of Chrome since it's closed source. I assumed GP meant chromium. A while back there was a chromium-bin for a short period, but it seems to have fallen out of maintenance and is now removed.
Oh man, I always install binary chrome-stable. Rust is another I don't enjoy building, so bin package there as well. But god forbid one of LLVM, QT and glibc chewing up all my CPU time every few months.
Truthfully, I never actually got to the rust build portion of the install. Rust required it's own patched version of LLVM to build, and I stopped there since I felt it was not worth compiling both, just for the one.