Unfortunately, I was unable to produce a repro without asm.js. In normal
JavaScript, the bounds check renaming saves us.

I have not done anything about the index variable aliasing and handling
of differently sized elements yet!

BUG=chromium:639210, v8:5266

Review-Url: https://codereview.chromium.org/2270793004
Cr-Commit-Position: refs/heads/master@{#38874}