Auto merge of #18271 - legnaleurc:propagate_dirty_bits, r=emilio

Propagate dirty bits after invalidation if needed.

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Follow up for [bug 1388298](https://bugzil.la/1388298).

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- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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components/style/invalidation/element/invalidator.rs

@@ -121,7 +121,7 @@ impl fmt::Debug for Invalidation {
 }
 
 /// The result of processing a single invalidation for a given element.
-struct InvalidationResult {
+struct SingleInvalidationResult {
     /// Whether the element itself was invalidated.
     invalidated_self: bool,
     /// Whether the invalidation matched, either invalidating the element or
@@ -129,6 +129,42 @@ struct InvalidationResult {
     matched: bool,
 }
 
+/// The result of a whole invalidation process for a given element.
+pub struct InvalidationResult {
+    /// Whether the element itself was invalidated.
+    invalidated_self: bool,
+    /// Whether the element's descendants were invalidated.
+    invalidated_descendants: bool,
+    /// Whether the element's siblings were invalidated.
+    invalidated_siblings: bool,
+}
+
+impl InvalidationResult {
+    /// Create an emtpy result.
+    pub fn empty() -> Self {
+        Self {
+            invalidated_self: false,
+            invalidated_descendants: false,
+            invalidated_siblings: false,
+        }
+    }
+
+    /// Whether the invalidation has invalidate the element itself.
+    pub fn has_invalidated_self(&self) -> bool {
+        self.invalidated_self
+    }
+
+    /// Whether the invalidation has invalidate desendants.
+    pub fn has_invalidated_descendants(&self) -> bool {
+        self.invalidated_descendants
+    }
+
+    /// Whether the invalidation has invalidate siblings.
+    pub fn has_invalidated_siblings(&self) -> bool {
+        self.invalidated_siblings
+    }
+}
+
 impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
     where E: TElement,
 {
@@ -148,7 +184,7 @@ impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
     }
 
     /// Perform the invalidation pass.
-    pub fn invalidate(mut self) {
+    pub fn invalidate(mut self) -> InvalidationResult {
         debug!("StyleTreeInvalidator::invalidate({:?})", self.element);
         debug_assert!(self.element.has_snapshot(), "Why bothering?");
         debug_assert!(self.data.is_some(), "How exactly?");
@@ -161,7 +197,7 @@ impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
         let snapshot = wrapper.snapshot().expect("has_snapshot lied");
 
         if !snapshot.has_attrs() && state_changes.is_empty() {
-            return;
+            return InvalidationResult::empty();
         }
 
         // If we are sensitive to visitedness and the visited state changed, we
@@ -258,8 +294,10 @@ impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
         debug!("Collected invalidations (self: {}): ", invalidated_self);
         debug!(" > descendants: {:?}", descendant_invalidations);
         debug!(" > siblings: {:?}", sibling_invalidations);
-        self.invalidate_descendants(&descendant_invalidations);
-        self.invalidate_siblings(&mut sibling_invalidations);
+        let invalidated_descendants = self.invalidate_descendants(&descendant_invalidations);
+        let invalidated_siblings = self.invalidate_siblings(&mut sibling_invalidations);
+
+        InvalidationResult { invalidated_self, invalidated_descendants, invalidated_siblings }
     }
 
     /// Go through later DOM siblings, invalidating style as needed using the
@@ -591,7 +629,7 @@ impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
         descendant_invalidations: &mut InvalidationVector,
         sibling_invalidations: &mut InvalidationVector,
         invalidation_kind: InvalidationKind,
-    ) -> InvalidationResult {
+    ) -> SingleInvalidationResult {
         debug!("TreeStyleInvalidator::process_invalidation({:?}, {:?}, {:?})",
                self.element, invalidation, invalidation_kind);
 
@@ -765,7 +803,7 @@ impl<'a, 'b: 'a, E> TreeStyleInvalidator<'a, 'b, E>
             }
         }
 
-        InvalidationResult { invalidated_self, matched, }
+        SingleInvalidationResult { invalidated_self, matched, }
     }
 }