Update V8 to version 4.9.134.

Summary of changes available at:
https://chromium.googlesource.com/v8/v8/+log/baf869df..42acdb73

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/1499603003

Cr-Commit-Position: refs/heads/master@{#363036}

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': 'baf869df700a81846de2a0fc9e06ee7d4d1f23e0',
+  'v8_revision': '42acdb73ff6b85f453d6ed549de79fe797417408',
   # 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.