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

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1 files changed, 13 insertions, 1 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 839fac79006..b44bbb54b96 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -103,7 +103,7 @@ use std::time::Duration;
 use style::animation::Animation;
 use style::context::{QuirksMode, RegisteredSpeculativePainter, RegisteredSpeculativePainters};
 use style::context::{SharedStyleContext, ThreadLocalStyleContextCreationInfo};
-use style::dom::{ShowSubtree, ShowSubtreeDataAndPrimaryValues, TElement, TNode};
+use style::dom::{ShowSubtree, ShowSubtreeDataAndPrimaryValues, TDocument, TElement, TNode};
 use style::driver;
 use style::error_reporting::RustLogReporter;
 use style::global_style_data::{GLOBAL_STYLE_DATA, STYLE_THREAD_POOL};
@@ -1346,6 +1346,18 @@ impl LayoutThread {
             }
         }
 
+        debug!(
+            "Shadow roots in document {:?}",
+            document.shadow_roots().len()
+        );
+
+        // Flush shadow roots stylesheets if dirty.
+        document.flush_shadow_roots_stylesheets(
+            &self.stylist.device(),
+            document.quirks_mode(),
+            guards.author.clone(),
+        );
+
         let restyles = document.drain_pending_restyles();
         debug!("Draining restyles: {}", restyles.len());