Don't shrink new space based on allocation rate in predictable mode.
Don't shrink new space based on allocation rate in predictable mode.

BUG=

Review URL: https://codereview.chromium.org/1155163003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#28618}

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