Update V8 to version 4.9.252.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/e298b698..c0a92294

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/1543783002

Cr-Commit-Position: refs/heads/master@{#366544}

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': 'e298b6983415758156c7567a2fbf625ca2c715c6',
+  'v8_revision': 'c0a92294de511bef32d503d0b629809a82d6f8bd',
   # 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.