2 files changed, 30 insertions, 3 deletions

diff --git a/components/layout_thread/dom_wrapper.rs b/components/layout_thread/dom_wrapper.rs
index bbc023cf958..1aa9488c327 100644
--- a/components/layout_thread/dom_wrapper.rs
+++ b/components/layout_thread/dom_wrapper.rs
@@ -83,6 +83,7 @@ use style::dom::{DomChildren, LayoutIterator, NodeInfo, OpaqueNode};
 use style::dom::{TDocument, TElement, TNode, TShadowRoot};
 use style::element_state::*;
 use style::font_metrics::ServoMetricsProvider;
+use style::media_queries::Device;
 use style::properties::{ComputedValues, PropertyDeclarationBlock};
 use style::selector_parser::{extended_filtering, PseudoElement, SelectorImpl};
 use style::selector_parser::{AttrValue as SelectorAttrValue, Lang, NonTSPseudoClass};
@@ -219,11 +220,16 @@ impl<'sr> ServoShadowRoot<'sr> {
         }
     }
 
-    pub fn flush_stylesheets(&self, guard: &SharedRwLockReadGuard) {
+    pub fn flush_stylesheets(
+        &self,
+        device: &Device,
+        quirks_mode: QuirksMode,
+        guard: &SharedRwLockReadGuard,
+    ) {
         unsafe {
             &self
                 .shadow_root
-                .flush_stylesheets::<ServoLayoutElement>(guard)
+                .flush_stylesheets::<ServoLayoutElement>(device, quirks_mode, guard)
         };
     }
 }
@@ -425,6 +431,16 @@ impl<'ld> ServoLayoutDocument<'ld> {
         unsafe { self.document.style_shared_lock() }
     }
 
+    pub fn shadow_roots(&self) -> Vec<ServoShadowRoot> {
+        unsafe {
+            self.document
+                .shadow_roots()
+                .iter()
+                .map(|sr| ServoShadowRoot::from_layout_js(*sr))
+                .collect()
+        }
+    }
+
     pub fn from_layout_js(doc: LayoutDom<Document>) -> ServoLayoutDocument<'ld> {
         ServoLayoutDocument {
             document: doc,
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 839fac79006..8c46fb90720 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 +1346,17 @@ impl LayoutThread {
             }
         }
 
+        debug!(
+            "Shadow roots in document {:?}",
+            document.shadow_roots().len()
+        );
+
+        let device = Device::new(MediaType::screen(), initial_viewport, device_pixel_ratio);
+        // Flush shadow roots stylesheets if dirty.
+        for shadow_root in document.shadow_roots() {
+            shadow_root.flush_stylesheets(&device, document.quirks_mode(), guards.author.clone());
+        }
+
         let restyles = document.drain_pending_restyles();
         debug!("Draining restyles: {}", restyles.len());