No? I don't understand how your question makes sense in relation to the GP comment. You can see the entirety of the diff here: https://bugs.webkit.org/attachment.cgi?id=224240&action=diff

I believe most of the shadow DOM stuff was removed almost a year ago after the Blink fork, because the maintainers of the code were leaving with Blink. eg

> Is anyone intending to maintain the feature on trunk? If not, we should simply get rid of code behind this build flag for now; keeping unmaintained code that doesn't even compile isn't healthy for the project of our size.[1]

It looks like this was just some last remaining code behind a leftover build flag.

[1] https://lists.webkit.org/pipermail/webkit-dev/2013-May/02489...