Rolling v8/tools/swarming_client to 8fce79620b04bbe5415ace1103db27505bdc4c06

TBR=machenbach@chromium.org,vogelheim@chromium.org,hablich@chromium.org

Review URL: https://codereview.chromium.org/1412173007

Cr-Commit-Position: refs/heads/master@{#31451}