Add slash to package dir URI after resolving reference against base.

Used to add slash to reference before resolving it.
It only makes a difference for the empty URI reference which
never makes sense anyway - this just ensures the error is the same
as on the VM. It is, arguably, what the specification requires.

R=sgjesse@google.com

Review URL: https://codereview.chromium.org//1297923004.
2 files changed
tree: 99f648558e2129fe20e1704bac6f820592538a1c
  1. pkgs/