Performance and stability improvements on all platforms.

TBR=v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com

Change-Id: I08cc6625eef048a3da003086675e23624a3f9e9c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1583182
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.29@{#1}
Cr-Branched-From: 6f7b8f627019067a3b83ac2c3301128a4ed47db9-refs/heads/master@{#60998}