This simplfies the code for lowering of {JSCreateArguments} nodes under
the assumption that deoptimization support is always enabled, and that
arguments objects are only materialized for JavaScript frames and not
for internal stub frames.

R=tebbi@chromium.org

Change-Id: I5f86ae0f0442a03b516904d737c5a0eac293b5b9
Reviewed-on: https://chromium-review.googlesource.com/640381Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47685}