Shadow-piercing combinators in the wild

Folks,

While doing research in preparation for the Web Components F2F in April
[1], I wrote up a summary of Blink's experiences with with the /deep/
combinator here:

https://github.com/w3c/webcomponents/wiki/Shadow-piercing-Combinators-in-the-Wild

I hope this WG will find it useful.

[1]:
https://lists.w3.org/Archives/Public/public-webapps/2015JanMar/0661.html

:DG<