Update V8 to version 6.0.293.

Update V8 to version 6.0.293.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/4f4da28e..67d79fa6

Please follow these instructions for assigning/CC'ing issues:
https://github.com/v8/v8/wiki/Triaging%20issues

Please close rolling in case of a roll revert:
https://v8-roll.appspot.com/
This only works with a Google account.

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

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

[v8-autoroll, 2017-05-22 14:02:21]

The CQ bit was checked by v8-autoroll@chromium.org

[commit-bot: I haz the power, 2017-05-22 14:02:42]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-22 15:38:57]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-22 15:38:58]

Try jobs failed on following builders:
  linux_optional_gpu_tests_rel on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_optional_...)

[v8-autoroll, 2017-05-22 15:45:10]

The CQ bit was checked by v8-autoroll@chromium.org

[commit-bot: I haz the power, 2017-05-22 15:45:29]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Michael Achenbach, 2017-05-22 16:33:34]

crashes possibly caused by https://chromium-review.googlesource.com/c/509570/

it was already reverted. So closing this and rolling forward...

[Michael Achenbach, 2017-05-22 16:33:39]

The CQ bit was unchecked by machenbach@chromium.org