Update V8 to version 4.9.277.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/1b50b896..8872babd

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.

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

Review URL: https://codereview.chromium.org/1554873002

Cr-Commit-Position: refs/heads/master@{#367241}

DEPS

@@ -43,7 +43,7 @@ vars = {
   # 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': '1b50b896c3032a0bcc14d916713946c6fe766b72',
+  'v8_revision': '8872babdc91c7d600a2ecfa036d5dd14af10606c',
   # 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.