Performance and stability improvements on all platforms.

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

Change-Id: Ib144030f3daec67318775f966275d83096ffd7ea
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1586841
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.56@{#1}
Cr-Branched-From: 411fd9cfd6ab3f7f46a030830b030bdca8fabb74-refs/heads/master@{#61061}