Make sure we have non-zero idle time even after rounding to size_t
Make sure we have non-zero idle time even after rounding to size_t

BUG=v8:3728
R=machenbach@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/764263002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#25578}

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