Make sure to compute visited style if our parent has visited style.

Part 4 of the fix for Gecko bug 1364242: https://bugzilla.mozilla.org/show_bug.cgi?id=1364242

components/style/matching.rs

@@ -151,7 +151,10 @@ impl CascadeVisitedMode {
     fn rules<'a>(&self, inputs: &'a CascadeInputs) -> &'a StrongRuleNode {
         match *self {
             CascadeVisitedMode::Unvisited => inputs.rules(),
-            CascadeVisitedMode::Visited => inputs.visited_rules(),
+            CascadeVisitedMode::Visited => match inputs.get_visited_rules() {
+                Some(rules) => rules,
+                None => inputs.rules(),
+            }
         }
     }
 
@@ -314,6 +317,9 @@ trait PrivateMatchMethods: TElement {
     /// pseudo-elements after collecting the appropriate rules to use.
     ///
     /// `primary_style` is expected to be Some for eager pseudo-elements.
+    ///
+    /// `parent_info` is our style parent and its primary style, if
+    /// it's already been computed.
     fn cascade_with_rules(&self,
                           shared_context: &SharedStyleContext,
                           font_metrics_provider: &FontMetricsProvider,
@@ -321,6 +327,7 @@ trait PrivateMatchMethods: TElement {
                           primary_style: Option<&Arc<ComputedValues>>,
                           cascade_target: CascadeTarget,
                           cascade_visited: CascadeVisitedMode,
+                          parent_info: Option<&ParentElementAndStyle<Self>>,
                           visited_values_to_insert: Option<Arc<ComputedValues>>)
                           -> Arc<ComputedValues> {
         let mut cascade_info = CascadeInfo::new();
@@ -343,9 +350,15 @@ trait PrivateMatchMethods: TElement {
         let element_and_style; // So parent_el and style_to_inherit_from are known live.
         let style_to_inherit_from = match cascade_target {
             CascadeTarget::Normal => {
-                element_and_style = self.get_inherited_style_and_parent();
-                parent_el = element_and_style.element;
-                element_and_style.style.as_ref().map(|s| cascade_visited.values(s))
+                let info = match parent_info {
+                    Some(element_and_style) => element_and_style,
+                    None => {
+                        element_and_style = self.get_inherited_style_and_parent();
+                        &element_and_style
+                    }
+                };
+                parent_el = info.element;
+                info.style.as_ref().map(|s| cascade_visited.values(s))
             }
             CascadeTarget::EagerPseudo => {
                 parent_el = Some(self.clone());
@@ -402,11 +415,15 @@ trait PrivateMatchMethods: TElement {
     /// pseudo-elements.
     ///
     /// `primary_style` is expected to be Some for eager pseudo-elements.
+    ///
+    /// `parent_info` is our style parent and its primary style, if
+    /// it's already been computed.
     fn cascade_internal(&self,
                         context: &StyleContext<Self>,
                         primary_style: Option<&Arc<ComputedValues>>,
                         primary_inputs: &CascadeInputs,
                         eager_pseudo_inputs: Option<&CascadeInputs>,
+                        parent_info: Option<&ParentElementAndStyle<Self>>,
                         cascade_visited: CascadeVisitedMode)
                         -> Arc<ComputedValues> {
         if let Some(pseudo) = self.implemented_pseudo_element() {
@@ -470,15 +487,19 @@ trait PrivateMatchMethods: TElement {
                                 primary_style,
                                 cascade_target,
                                 cascade_visited,
+                                parent_info,
                                 visited_values_to_insert)
     }
 
     /// Computes values and damage for the primary style of an element, setting
     /// them on the ElementData.
+    ///
+    /// `parent_info` is our style parent and its primary style.
     fn cascade_primary(&self,
                        context: &mut StyleContext<Self>,
                        data: &mut ElementData,
                        important_rules_changed: bool,
+                       parent_info: &ParentElementAndStyle<Self>,
                        cascade_visited: CascadeVisitedMode)
                        -> ChildCascadeRequirement {
         debug!("Cascade primary for {:?}, visited: {:?}", self, cascade_visited);
@@ -496,7 +517,10 @@ trait PrivateMatchMethods: TElement {
             // visited case. This early return is especially important for the
             // `cascade_primary_and_pseudos` path since we rely on the state of
             // some previous matching run.
-            if !cascade_visited.has_rules(primary_inputs) {
+            //
+            // Note that we cannot take this early return if our parent has
+            // visited style, because then we too have visited style.
+            if !cascade_visited.has_rules(primary_inputs) && !parent_info.has_visited_style() {
                 return ChildCascadeRequirement::CanSkipCascade
             }
 
@@ -505,6 +529,7 @@ trait PrivateMatchMethods: TElement {
                                   None,
                                   primary_inputs,
                                   None,
+                                  /* parent_info = */ None,
                                   cascade_visited)
         };
 
@@ -593,6 +618,7 @@ trait PrivateMatchMethods: TElement {
                                   data.styles.get_primary(),
                                   primary_inputs,
                                   Some(pseudo_inputs),
+                                  /* parent_info = */ None,
                                   cascade_visited)
         };
 
@@ -636,6 +662,7 @@ trait PrivateMatchMethods: TElement {
                                      Some(primary_style),
                                      CascadeTarget::Normal,
                                      CascadeVisitedMode::Unvisited,
+                                     /* parent_info = */ None,
                                      None))
     }
 
@@ -899,6 +926,12 @@ struct ParentElementAndStyle<E: TElement> {
     style: Option<Arc<ComputedValues>>,
 }
 
+impl<E: TElement> ParentElementAndStyle<E> {
+    fn has_visited_style(&self) -> bool {
+        self.style.as_ref().map_or(false, |v| { v.get_visited_style().is_some() })
+    }
+}
+
 /// Collects the outputs of the primary matching process, including the rule
 /// node and other associated data.
 #[derive(Debug)]
@@ -966,13 +999,21 @@ pub trait MatchMethods : TElement {
         let relevant_link_found = primary_results.relevant_link_found;
         if relevant_link_found {
             self.match_primary(context, data, VisitedHandlingMode::RelevantLinkVisited);
+        }
+
+        // Even if there is no relevant link, we need to cascade visited styles
+        // if our parent has visited styles.
+        let parent_and_styles = self.get_inherited_style_and_parent();
+        if relevant_link_found || parent_and_styles.has_visited_style() {
             self.cascade_primary(context, data, important_rules_changed,
+                                 &parent_and_styles,
                                  CascadeVisitedMode::Visited);
         }
 
         // Cascade properties and compute primary values.
         let child_cascade_requirement =
             self.cascade_primary(context, data, important_rules_changed,
+                                 &parent_and_styles,
                                  CascadeVisitedMode::Unvisited);
 
         // Match and cascade eager pseudo-elements.
@@ -1039,10 +1080,13 @@ pub trait MatchMethods : TElement {
         // visited ComputedValues are placed within the regular ComputedValues,
         // which is immutable after the cascade.  If there aren't any visited
         // rules, these calls will return without cascading.
+        let parent_and_styles = self.get_inherited_style_and_parent();
         self.cascade_primary(context, &mut data, important_rules_changed,
+                             &parent_and_styles,
                              CascadeVisitedMode::Visited);
         let child_cascade_requirement =
             self.cascade_primary(context, &mut data, important_rules_changed,
+                                 &parent_and_styles,
                                  CascadeVisitedMode::Unvisited);
         self.cascade_pseudos(context, &mut data, CascadeVisitedMode::Visited);
         self.cascade_pseudos(context, &mut data, CascadeVisitedMode::Unvisited);
@@ -1611,6 +1655,7 @@ pub trait MatchMethods : TElement {
                                 Some(primary_style),
                                 CascadeTarget::Normal,
                                 CascadeVisitedMode::Unvisited,
+                                /* parent_info = */ None,
                                 None)
     }