Instead of wriring the elements kind transitions into the control flow
early on, we do instead put this marker into the effect chain, so that
the elements transitions are visible to the LoadElimination and can
thus be optimized properly there.

This CL itself doesn't add any of those optimizations, but just adds
the foundations to make them possible later.

R=jarin@chromium.org
BUG=v8:4930,v8:5141

Review-Url: https://codereview.chromium.org/2164573003
Cr-Commit-Position: refs/heads/master@{#37869}