Update V8 to version 6.0.66.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/9f6be2e9..ab1af916

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

Review-Url: https://codereview.chromium.org/2837923002
Cr-Commit-Position: refs/heads/master@{#466756}
diff --git a/DEPS b/DEPS
index 6b748a3..a44a0cce 100644
--- a/DEPS
+++ b/DEPS
@@ -44,7 +44,7 @@
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.
-  'v8_revision': '9f6be2e9e4279586cf484b669d1fc701c31a7fe2',
+  'v8_revision': 'ab1af916c23dfdb933831490fd2f5133bdd0fef6',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling swarming_client
   # and whatever else without interference from each other.