No need to keep bundled protobuf.
Switch to USES=execinfo
Miscellaneous nits.
Fix and enhance installation, ideas from OpenBSD:
- install all available icons (except the b/w and named versions)
- install chrome binary and ffmpegsumo library as such
- install keyboard_resources.pak
- fix installation of chrome-wrapper
- do not install bundled xdg-settings (does not exist anymore)
- install mksnapshot binary
- regenerate pkg-plist