This is a reland of e877b177

Original change's description:
> gclient: Get rid of parsed_url.
>
> There is no reason I can see to set parsed_url so late.
> Also, the tests are misleading, since relative URLs don't behave the way
> the tests led you to believe.
>
> Bug: 839925
> Change-Id: I08d92b7b7847bdc406f003d4a4139d968cc662b1
> Reviewed-on: https://chromium-review.googlesource.com/1047797
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Marc-Antoine Ruel <maruel@chromium.org>

TBR=agable@chromium.org

Bug: 839925
Change-Id: I9200ec5fbe7289022e9754f0c78676dc931fcaeb
Reviewed-on: https://chromium-review.googlesource.com/1054567
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>