Performance and stability improvements on all platforms.

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

Change-Id: I3a8da2ecde102b5339aaf87c39e2f3687d8c1d31
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1611742
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.176@{#1}
Cr-Branched-From: 37ab663ae5c6ecfea569c00b27ace7c38402088a-refs/heads/master@{#61472}