This was a shim for the non-I+TF codepath, which is now the only
codepath (that still uses this tier-up mechanism anyway). There were a
couple of places we were accidentally using it due to CompileLazy or
deopts, so this also fixes those.

Change-Id: I00a7fdf9fb5cf74844138dac62d01ceaaf192e17
Reviewed-on: https://chromium-review.googlesource.com/951490
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51786}