In LoadElimination, don't consider two fields as potentially
aliasing if they have different names.

This gives another 5% boost on the Octane/DeltaBlue benchmark,
since the redundant loads and checks on the elms of the
OrderedCollection can be properly eliminated in the chainTest.

Bug: v8:5267
Change-Id: Id2dbb8cac02f9c95a85e5cc8acac3f66b679fd06
Reviewed-on: https://chromium-review.googlesource.com/620727Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47424}