Updating test from legacy harness

Updating some tests in fast/workers from the legacy test harness to
testharness.js in preparation to be upstreamed to external/wpt/workers.

Bug: 795636
Change-Id: I0ccda4a23d6ac54c34fe60613ce6559d6681434d
Reviewed-on: https://chromium-review.googlesource.com/c/1451424
Commit-Queue: Katie Dillon <kdillon@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631812}
24 files changed