Performance and stability improvements on all platforms.

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

Change-Id: I5e10447e23db81462e42c9a6ddb535e5af75b8f9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1600591
Reviewed-by: v8-ci-autoroll-builder <v8-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/7.6.119@{#1}
Cr-Branched-From: 0b830b328afc74eea41d4ef45e3aa2d89ca4f51a-refs/heads/master@{#61311}