Shorten the name of virtual/off-main-thread-worker-script-fetch

The long virtual test name caused crbug.com/906964 due to path length
limit exceeded.

Bug: 880027, 906964
Change-Id: I63cf49387adecf2f9e729ee10b26ffd86971cf8d
Reviewed-on: https://chromium-review.googlesource.com/c/1344579
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610901}
5 files changed