Should help the case where the single existing transition matches.

BUG=v8:8547

Change-Id: Ic459357a10311346499ea054447d6cc42352fc0d
Reviewed-on: https://chromium-review.googlesource.com/c/1363133Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58090}