Those two tests fail in gc-stress and custom snapshot (embedding mjsunit.js).
This is likely due to different GC timing with the custom snapshot.

R=mstarzinger@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1078653002

Cr-Commit-Position: refs/heads/master@{#27688}