When the slow path for Array.prototype.indexOf calls a Proxy's "has"
trap, it must check afterwards whether an exception was thrown.

BUG=chromium:728813

Change-Id: I998bba6ddcd65adfed2eefb63b3285da60d2a43c
Reviewed-on: https://chromium-review.googlesource.com/527173Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45759}