Run more tests on Fuchsia bots.

Adds ipc_tests, media_unittests, sql_unittests to
the CQ fuchsia_x64 bot, where they all seem to pass.

Add comments to the net_unittests suppressions explaining why they're
there.

Also adds these tests and content_unittests to some Fuchsia FYI
bots (which don't have cq bots, so I don't know if they pass --
if not, we can disable them again).

There is no comment explaining why these are disabled, and since
they pass, let's run them.

Bug: 843511,847915,844416
Change-Id: Ife31eeb61a6e505e5e2c0b9a4efeda0af34e4d9f
Reviewed-on: https://chromium-review.googlesource.com/1120753
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573299}
3 files changed