fuchsia: Fix field trial shm serialization, enable FieldTrialListTest.*

Mostly fixed by https://chromium-review.googlesource.com/c/545148/.
After also fixing the handle serialization, the associated tests all
pass.

Bug: 706592
Change-Id: I996a7463b10774c57123e5ae0f06e0d841035de8
Reviewed-on: https://chromium-review.googlesource.com/546900
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483253}
2 files changed