Performance and stability improvements on all platforms.

[email protected]

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I544e851e47050f9ffa2dc93e72f134e6b79b42c5
Reviewed-on: https://chromium-review.googlesource.com/902722
Reviewed-by: v8 autoroll <[email protected]>
Cr-Commit-Position: refs/heads/6.6.164@{#1}
Cr-Branched-From: 84504c2a91bf029dd8030ece37b81fadc2811750-refs/heads/master@{#51102}