This repairs the performance regression on Octane/EarleyBoyer and
JetStream/EarleyBoyer benchmarks.

Bug: chromium:772268, v8:6367, v8:6278, v8:6344
Change-Id: Ibc144a35b37c5822f88712550d8db09386241341
Reviewed-on: https://chromium-review.googlesource.com/704574Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48326}