When the bailout triggered, we assumed we're generating data (i.e., we're inside
a non-arrow function). This is not true; it's possible that we're already inside
an arrow function and not generating data anyway.

BUG=v8:5516,chromium:761980

Change-Id: Iad9c8dde283031630953ef9a46c1e68bc0cee048
Reviewed-on: https://chromium-review.googlesource.com/655081Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47905}