Performance and stability improvements on all platforms.

[email protected]

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I57c34411d0e3e33518f0b2102367eaee4a512c05
Reviewed-on: https://chromium-review.googlesource.com/889950
Reviewed-by: v8 autoroll <[email protected]>
Cr-Commit-Position: refs/heads/6.6.89@{#1}
Cr-Branched-From: 6ecd9702269f386349ba8ba8ad97ac91c69441f8-refs/heads/master@{#50914}