This fixes a rendering issue on https://prodengi.kz/ that someone on
Discord reported. :^)
(cherry picked from commit 0b775da7c72a85c099f35d8caf2e7b66721a4483)
Instead of trying to locate the relevant StyleSheetList on style element
removal from the DOM, we now simply keep a pointer to the list instead.
This fixes an issue where using attachShadow() on an element that had
a declarative shadow DOM would cause any style elements present to use
the wrong StyleSheetList when removing themselves from the tree.
(cherry picked from commit 8543b8ad6a4d96bd0c247052572b8c2abf3929a7)
Before this change, :hover wouldn't match anything outside the shadow
boundary when hovering elements inside a shadow tree. This was most
noticeable when hovering the text inside an input element and hover
styles disappearing from the hosting input element itself.
(cherry picked from commit 84ab8bf7973147d054a99445943b9da930ceb0a2)
Before this change, removing a style element from inside a shadow tree
would cause it to be unregistered with the document-level list of sheets
instead of the shadow-root-level list.
This would eventually lead to a verification failure if someone tried to
update the text contents of that style element, since it was still in
the shadow-root-level list, but now with a null owner element.
Fixes a crash on https://www.swedbank.se/
(cherry picked from commit 3b7534b3628641244b0998fd5061c6fa75a61cf5)
