[turbofan] Workaround inconsistency of the type system.
[turbofan] Workaround inconsistency of the type system.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/770193002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#25594}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh