If a statement or expression does not produce any bytecode, it's position
should always be overwritten by a following statement position.

R=mstarzinger@chromium.org, vogelheim@chromium.org
BUG=v8:4680
LOG=N

Review URL: https://codereview.chromium.org/1854113002

Cr-Commit-Position: refs/heads/master@{#35252}