On: Opera, Brave, Vivaldi to ignore Chrome's anti-ad-blocker changes

[metildaa]

Note that this was done after two prior failed attempts to rewrite the CSS engine for multithread in C++: https://hacks.mozilla.org/2019/02/rewriting-a-browser-compon...

Its sad to lose DownThemAll and the plethora of othwr XUL extensions, but having performant multicore support is critical given the shift to having many cores (as single thread performance improvements become uncommon).