Auto merge of #22743 - ferjm:shadowdom, r=emilio

Partial ShadowDOM support

This is just an early WIP, not to take it very seriously yet.

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [x] These changes fix #22719
- [x] There are tests for these changes

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/22743)
<!-- Reviewable:end -->

1 files changed, 10 insertions, 2 deletions

diff --git a/components/script/stylesheet_loader.rs b/components/script/stylesheet_loader.rs
index 61c89b35f80..69975c7803b 100644
--- a/components/script/stylesheet_loader.rs
+++ b/components/script/stylesheet_loader.rs
@@ -13,8 +13,9 @@ use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::htmlelement::HTMLElement;
 use crate::dom::htmllinkelement::{HTMLLinkElement, RequestGenerationId};
-use crate::dom::node::{document_from_node, window_from_node};
+use crate::dom::node::{containing_shadow_root, document_from_node, window_from_node};
 use crate::dom::performanceresourcetiming::InitiatorType;
+use crate::dom::shadowroot::ShadowRoot;
 use crate::network_listener::{self, NetworkListener, PreInvoke, ResourceTimingListener};
 use cssparser::SourceLocation;
 use encoding_rs::UTF_8;
@@ -81,6 +82,7 @@ pub struct StylesheetContext {
     data: Vec<u8>,
     /// The node document for elem when the load was initiated.
     document: Trusted<Document>,
+    shadow_root: Option<Trusted<ShadowRoot>>,
     origin_clean: bool,
     /// A token which must match the generation id of the `HTMLLinkElement` for it to load the stylesheet.
     /// This is ignored for `HTMLStyleElement` and imports.
@@ -187,7 +189,11 @@ impl FetchResponseListener for StylesheetContext {
                 },
             }
 
-            document.invalidate_stylesheets();
+            if let Some(ref shadow_root) = self.shadow_root {
+                shadow_root.root().invalidate_stylesheets();
+            } else {
+                document.invalidate_stylesheets();
+            }
 
             // FIXME: Revisit once consensus is reached at:
             // https://github.com/whatwg/html/issues/1142
@@ -264,6 +270,7 @@ impl<'a> StylesheetLoader<'a> {
         integrity_metadata: String,
     ) {
         let document = document_from_node(self.elem);
+        let shadow_root = containing_shadow_root(self.elem).map(|sr| Trusted::new(&*sr));
         let gen = self
             .elem
             .downcast::<HTMLLinkElement>()
@@ -275,6 +282,7 @@ impl<'a> StylesheetLoader<'a> {
             metadata: None,
             data: vec![],
             document: Trusted::new(&*document),
+            shadow_root,
             origin_clean: true,
             request_generation_id: gen,
             resource_timing: ResourceFetchTiming::new(ResourceTimingType::Resource),