chromium: Prepare for building the -lite package.

We currently can't build the -lite package because beta and dev versions
aren't yet compatible with ICU version 52. But apart from that blocker,
this should get us ready for the switch.

Also, we're now correctly unbundling all dependencies which are used
from <nixpkgs>.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>