Now just accumulate right before we might validate a property and once we're
done, so we're guaranteed to catch all PatternErrors.

Bug: v8:8607
Change-Id: Ibc5bc7773756f4827868ca01d0f9fb0c5545e59b
Reviewed-on: https://chromium-review.googlesource.com/c/1382749
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58343}