Let SVGStyleElement delegate style updates through StyleElementBase so
parser-created inline SVG `<style>` elements update when they are popped
from the parser stack, just like HTML style elements.
This lets SVG style imports participate in script-blocking stylesheet
checks while keeping dynamic text, type, and media changes from
re-blocking parser scripts.
Evaluate the associated stylesheet's media queries when a parser-created
`<style>` sheet is created, and re-evaluate them when the media
attribute changes.
This lets HTMLStyleElement::contributes_a_script_blocking_style_sheet()
honor the media clause from the HTML script-blocking rules. A
still-loading parser-created style is removed from the script-blocking
set as soon as its media no longer matches.
Create parser-blocking style sheets when parser-created `<style>`
elements are popped from the stack of open elements, and ignore dynamic
style updates while those elements are still open in the parser.
Make the shared style-element script-blocking predicate describe the
active style sheet instance. Stale script-blocking entries are removed
when that style sheet is replaced or removed.
