There are similar issues here: https://bugs.chromium.org/p/v8/issues/detail?id=4437#c6 - the environment seems to be different on swarming in regards to intl.

For the repro attempt above, you need the full set of flags to the driver so that it unpacks test262, e.g.:
tools/run-tests.py  --mode Debug --arch x64 --outdir out --buildbot --timeout=200 --random-seed=984594427 test262 --download-data --exhaustive-variants --rerun-failures-count=2 --swarming
(but it still doesn't repro)

I also tried the swarming repro command, to avoid any flag inconsistencies (it also doesn't repro):
python swarming.py reproduce -S https://chromium-swarm.appspot.com 2e32f55cae30b110 --output-dir output

To make sure it fails consistently on swarming, I also pressed retry to get another task:
https://chromium-swarm.appspot.com/user/task/2e41f2b0dfd88d10

Commented on https://bugs.chromium.org/p/v8/issues/detail?id=4437. The bots aren't started in a proper UI context.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/9c927d0f01acd5b8e6029b0eea0cca41b8e66973

commit 9c927d0f01acd5b8e6029b0eea0cca41b8e66973
Author: machenbach <machenbach@chromium.org>
Date: Tue Apr 19 11:26:21 2016

[test] Set default locale in test runner

BUG= v8:4437 , v8:2899 , chromium:604310 
LOG=n

Review URL: https://codereview.chromium.org/1402373002

Cr-Commit-Position: refs/heads/master@{#35614}

[modify] https://crrev.com/9c927d0f01acd5b8e6029b0eea0cca41b8e66973/test/intl/intl.status
[modify] https://crrev.com/9c927d0f01acd5b8e6029b0eea0cca41b8e66973/test/test262/test262.status
[modify] https://crrev.com/9c927d0f01acd5b8e6029b0eea0cca41b8e66973/tools/run-tests.py

The general issue is fixed by the CL above. Now swarming uses a default locale.

I don't know if it's worth spending time trying to repro the crash from the other CL by maybe letting the local machine _miss_ a locale?