... instead of creating a new one in each recursive call.

R=adamk@chromium.org

Bug: v8:1569
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ieb2e76a5dec7bc0157b534a8b5f21acf6c86007c
Reviewed-on: https://chromium-review.googlesource.com/552548Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46294}