Hello WebKit-dev,

We've been working on CSS Containment performance for a while.
Here is our summary of it, please take a look if you are interested. Thanks!
https://docs.google.com/document/d/166CsE0BqOGur1UyeMqxC7OSijeH90R1Pdck54rLgZNU/edit?usp=sharing

Regarding the current state of CSS contain, the implement of layout, size, paint and style containment
have been landed [1]. And the CSS contain runtime flag is enabled by default now [2]. \o/

[1] https://bugs.webkit.org/show_bug.cgi?id=172026

[2] https://bugs.webkit.org/show_bug.cgi?id=234020

Best,
Rob and Cathie