Unofficial gardening. fast/js/regress/HashMap-put-get-iterate-keys.html got slower after the most recent V8 roll.

BUG=259934
TBR=eseidel

Review URL: https://codereview.chromium.org/19060003

git-svn-id: svn://svn.chromium.org/blink/trunk@154137 bbb929c8-8fbe-4397-9dbb-9b2b20218538