PrepareElementsForSort must return a number less than or equal the array
length.

Bug: chromium:897512, v8:7382
Change-Id: If5f9c4d052e623ab9f3300b8534603abbee859fa
Reviewed-on: https://chromium-review.googlesource.com/c/1297958
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56982}