R=rmcilroy@chromium.org

Bug: v8:6409
Change-Id: I8205ca3e9587f4cb1d35d7edc1aa320814020ac4
Reviewed-on: https://chromium-review.googlesource.com/616665Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47387}