V8 used to erroneously allow ForStatements to contain a function
declaration, but that hasn't been true since we shipped the
"--harmony-restrictive-declarations" flag 1.5 years ago.

Bug: v8:4824
Change-Id: I893b45aed468017f89c0c5964df2091bea030327
Reviewed-on: https://chromium-review.googlesource.com/621871Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47553}