This improves delta blue by about >5%. Unfortunately, this still does not help load
and check elimination because we do not learn maps from control flow.

Change-Id: I49a97dbc40576b9bc80c87ec2b459e37ba9b4440
Bug: v8:5267
Reviewed-on: https://chromium-review.googlesource.com/618328
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47405}