base: Disable JSONPerfTest.StressTest

Disable JSONPerfTest.StressTest as it is still timing out even after
increasing the timeout.

TBR=gab@chromium.org

Bug: 906686
Change-Id: I67434e2405f86fd7f0fe9d82a901e618ac0b2b9e
Reviewed-on: https://chromium-review.googlesource.com/c/1378144
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616756}
1 file changed