For statementlists we only need to track whether they are null or not. We
especially do not need to track possible variable declarations.

Change-Id: I66377521c924931a1871e5df0e55a7b45f169155
Reviewed-on: https://chromium-review.googlesource.com/1249267Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56272}