This was missed in the original CL switching |is_posix| to false for
Fuchsia.

Bug: chromium:812974
Change-Id: I532516296c6b6ece9805c2f986c8dded00a798df
Reviewed-on: https://chromium-review.googlesource.com/1011251Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52599}