Performance and stability improvements on all platforms.

[email protected]

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Icb59aa631f6042d7118f04ff74ced57783005f4b
Reviewed-on: https://chromium-review.googlesource.com/807888
Reviewed-by: v8 autoroll <[email protected]>
Cr-Commit-Position: refs/heads/6.5.8@{#1}
Cr-Branched-From: 99b5f699abda3e470e0d22a8d48f6bd4a9976895-refs/heads/master@{#49851}