We only optimize functions which are already compiled, so there is no need
to ensure baseline in pipeline.cc, and since ast-graph-builder doesn't
do inlining, there are no other uses.

BUG=v8:5203, v8:6409

Change-Id: I830c8868d50363f61193a96d9a5774e059a1af0e
Reviewed-on: https://chromium-review.googlesource.com/570033
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46649}