Update V8 to version 6.3.180.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/9c5a43d3..b7b0ee77

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

Change-Id: Ie5fac1dbe5bdd7999dfee116d5bfdde3f4722bff
Reviewed-on: https://chromium-review.googlesource.com/672604
Reviewed-by: v8 autoroll <v8-autoroll@chromium.org>
Commit-Queue: v8 autoroll <v8-autoroll@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502858}
diff --git a/DEPS b/DEPS
index 794ad17..e2286b2 100644
--- a/DEPS
+++ b/DEPS
@@ -45,7 +45,7 @@
   # 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': '9c5a43d39d6c1ec5567ee15430008b5d52ce1837',
+  'v8_revision': 'b7b0ee77529aa896ab61c1e15ad3e0a3c093dbc8',
   # 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.