This is a reland of ff622244
should_process was set to None in the previous attempt, so CIPD dependencies were not processed.
This CL fixed that.

Original change's description:
> Reland "Expand variables in gclient flattened output."
>
> This is a reland of a32f98e6
>
> Original change's description:
> > Expand variables in gclient flattened output.
> >
> > Bug: 848990
> > Change-Id: I0ad7e4f965973edbc5a335bd30f9cbd7b04abff2
> > Reviewed-on: https://chromium-review.googlesource.com/1085996
> > Reviewed-by: Michael Moss <mmoss@chromium.org>
> > Reviewed-by: Aaron Gable <agable@chromium.org>
> > Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
>
> Tbr: agable@chromium.org
> Bug: 848990
> Change-Id: I7843544b79b2ab7e2046c187d13ea3eb65fc1b7d
> Reviewed-on: https://chromium-review.googlesource.com/1085975
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

Bug: 848990
Change-Id: Ic804be1b84bf8402a741a4189b60372075dfb6f3
Reviewed-on: https://chromium-review.googlesource.com/1087368Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>