Performance and stability improvements on all platforms.

[email protected]

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I9406a3597a7f9c27e22dd0be85deb362c0bf83aa
Reviewed-on: https://chromium-review.googlesource.com/748064
Reviewed-by: v8 autoroll <[email protected]>
Cr-Commit-Position: refs/heads/6.4.181@{#1}
Cr-Branched-From: d521a1e26106804c86758320db8544b53f934804-refs/heads/master@{#49061}