[code coverage] Run fuzzer against isolated corpus

This CL changes the script to use the isolated corpus instead of
downloading using gsutil.

Bug: 919565
Change-Id: I09990dd24db5248cca6a2158773bdec540908d6b
Reviewed-on: https://chromium-review.googlesource.com/c/1404418
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Shuotao Gao <stgao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621431}
1 file changed