Simplified lowering may loose feedback by inserting Checked
conversions for BoundsChecks in case the bounds check gets
optimized away later on.

Bug: v8:7127
Change-Id: I254a29ba4e578d653d1dee2d70582ce0a4b57789
Reviewed-on: https://chromium-review.googlesource.com/878743Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50783}