Flush shadow roots stylesheets only if they changed

2 files changed, 22 insertions, 7 deletions

diff --git a/components/layout_thread/dom_wrapper.rs b/components/layout_thread/dom_wrapper.rs
index 7ea68e6e3a2..72cbdf04701 100644
--- a/components/layout_thread/dom_wrapper.rs
+++ b/components/layout_thread/dom_wrapper.rs
@@ -437,6 +437,23 @@ impl<'ld> ServoLayoutDocument<'ld> {
         }
     }
 
+    pub fn flush_shadow_roots_stylesheets(
+        &self,
+        device: &Device,
+        quirks_mode: QuirksMode,
+        guard: &SharedRwLockReadGuard,
+    ) {
+        unsafe {
+            if !self.document.shadow_roots_styles_changed() {
+                return;
+            }
+            self.document.flush_shadow_roots_stylesheets();
+            for shadow_root in self.shadow_roots() {
+                shadow_root.flush_stylesheets(device, quirks_mode, guard);
+            }
+        }
+    }
+
     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 3ed2624d2d3..b44bbb54b96 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -1352,13 +1352,11 @@ impl LayoutThread {
         );
 
         // Flush shadow roots stylesheets if dirty.
-        for shadow_root in document.shadow_roots() {
-            shadow_root.flush_stylesheets(
-                &self.stylist.device(),
-                document.quirks_mode(),
-                guards.author.clone(),
-            );
-        }
+        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());