This addresses a TODO about the correct location of the helper function
in question, it is now internal to TurboFan instead of being shared.

R=jarin@chromium.org

Change-Id: I7e6112e9bc9759255a416fa2e2a9f92a8e4248c8
Reviewed-on: https://chromium-review.googlesource.com/542840Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46086}