This allows to reuse the class e.g. in the baseline compiler.

R=titzer@chromium.org

Change-Id: I7251af16e8c74f267834a9cefb676edf3c9f3a07
Reviewed-on: https://chromium-review.googlesource.com/570020Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46735}