This changes how rewind upon preparser abort works. It now rewinds to the start
of the parameter scope. In the case of "function X(" it is before the "(". In
the case of arrow functions it's before the start of the arrow function. This
allows us to reparse the arrow function from the start so all parameters are
declared properly.

Bug: v8:2728, v8:7390
Change-Id: I1c40056a49ec198560e63cd73949a59221ee0401
Reviewed-on: https://chromium-review.googlesource.com/c/1382736Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58332}