style: Make invalidation state also be with the ::slotted rules.

MozReview-Commit-ID: GYmsXYvL9vj

components/style/dom.rs

@@ -31,7 +31,7 @@ use std::fmt;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::ops::Deref;
-use stylist::Stylist;
+use stylist::{StyleRuleCascadeData, Stylist};
 use traversal_flags::TraversalFlags;
 
 /// An opaque handle to a node, which, unlike UnsafeNode, cannot be transformed
@@ -774,6 +774,41 @@ pub trait TElement
         false
     }
 
+    /// Executes the callback for each applicable style rule data which isn't
+    /// the main document's data (which stores UA / author rules).
+    ///
+    /// Returns whether normal document author rules should apply.
+    fn each_applicable_non_document_style_rule_data<'a, F>(&self, mut f: F) -> bool
+    where
+        Self: 'a,
+        F: FnMut(AtomicRef<'a, StyleRuleCascadeData>, QuirksMode),
+    {
+        let cut_off_inheritance = self.each_xbl_stylist(|stylist| {
+            let quirks_mode = stylist.quirks_mode();
+            f(
+                AtomicRef::map(stylist, |stylist| stylist.normal_author_cascade_data()),
+                quirks_mode,
+            )
+        });
+
+        let mut current = self.assigned_slot();
+        while let Some(slot) = current {
+            slot.each_xbl_stylist(|stylist| {
+                let quirks_mode = stylist.quirks_mode();
+                if stylist.slotted_author_cascade_data().is_some() {
+                    f(
+                        AtomicRef::map(stylist, |stylist| stylist.slotted_author_cascade_data().unwrap()),
+                        quirks_mode,
+                    )
+                }
+            });
+
+            current = slot.assigned_slot();
+        }
+
+        cut_off_inheritance
+    }
+
     /// Gets the current existing CSS transitions, by |property, end value| pairs in a FnvHashMap.
     #[cfg(feature = "gecko")]
     fn get_css_transitions_info(&self)