To stay compatible with JSC, Array.p.sort did a post-processing step
that shadowed elements from the prototype chain.

Some time ago, JSC changed and no longer exhibits this behavior. To
preserve comptibility and stay consistent with RemoveArrayHoles,
this CL removes this post-processing step altogether and adjusts
tests to expect the new behavior.

R=cbruni@chromium.org, jgruber@chromium.org

Bug: v8:7382
Change-Id: Iecedc37cea25001d3768b99a3a9de3a2db90ba82
Reviewed-on: https://chromium-review.googlesource.com/1047286
Commit-Queue: Simon Zünd <szuend@google.com>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53066}