Check ElementHasAnimations before trying to get animations rules.

In case of ::before and ::after element, the generated content has no
ElementHasAnimations flag, their parent has the flag.

components/style/dom.rs

@@ -506,6 +506,11 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
     /// Returns true if the element has all the specified selector flags.
     fn has_selector_flags(&self, flags: ElementSelectorFlags) -> bool;
 
+    /// In Gecko, element has a flag that represents the element may have
+    /// any type of animations or not to bail out animation stuff early.
+    /// Whereas Servo doesn't have such flag.
+    fn may_have_animations(&self) -> bool { false }
+
     /// Creates a task to update various animation state on a given (pseudo-)element.
     #[cfg(feature = "gecko")]
     fn update_animations(&self,

components/style/gecko/wrapper.rs

@@ -422,11 +422,6 @@ impl<'le> GeckoElement<'le> {
         }
     }
 
-    #[inline]
-    fn may_have_animations(&self) -> bool {
-        self.as_node().get_bool_flag(nsINode_BooleanFlag::ElementHasAnimations)
-    }
-
     #[inline]
     fn has_id(&self) -> bool {
         self.as_node().get_bool_flag(nsINode_BooleanFlag::ElementHasID)
@@ -777,6 +772,11 @@ impl<'le> TElement for GeckoElement<'le> {
         (self.flags() & node_flags) == node_flags
     }
 
+    #[inline]
+    fn may_have_animations(&self) -> bool {
+        self.as_node().get_bool_flag(nsINode_BooleanFlag::ElementHasAnimations)
+    }
+
     fn update_animations(&self,
                          before_change_style: Option<Arc<ComputedValues>>,
                          tasks: UpdateAnimationsTasks) {

components/style/matching.rs

@@ -254,12 +254,15 @@ trait PrivateMatchMethods: TElement {
             // We could make that a bit better if the complexity cost is not too
             // big, but given further restyles are posted directly to
             // pseudo-elements, it doesn't seem worth the effort at a glance.
-            if pseudo.is_eager() && primary_style.rules.get_animation_rules().is_empty() {
+            if pseudo.is_eager() {
                 let parent = self.parent_element().unwrap();
-                let parent_data = parent.borrow_data().unwrap();
+                if !parent.may_have_animations() ||
-                let pseudo_style =
+                   primary_style.rules.get_animation_rules().is_empty() {
-                    parent_data.styles().pseudos.get(&pseudo).unwrap();
+                    let parent_data = parent.borrow_data().unwrap();
-                return pseudo_style.values().clone()
+                    let pseudo_style =
+                        parent_data.styles().pseudos.get(&pseudo).unwrap();
+                    return pseudo_style.values().clone()
+                }
             }
         }
 
@@ -692,7 +695,7 @@ pub trait MatchMethods : TElement {
                 let pseudo_style =
                     parent_data.styles().pseudos.get(&pseudo).unwrap();
                 let mut rules = pseudo_style.rules.clone();
-                {
+                if parent.may_have_animations() {
                     let animation_rules = data.get_animation_rules();
 
                     // Handle animations here.
@@ -739,7 +742,11 @@ pub trait MatchMethods : TElement {
         let style_attribute = self.style_attribute();
         {
             let smil_override = data.get_smil_override();
-            let animation_rules = data.get_animation_rules();
+            let animation_rules = if self.may_have_animations() {
+                data.get_animation_rules()
+            } else {
+                AnimationRules(None, None)
+            };
             let bloom = context.thread_local.bloom_filter.filter();
 
             let map = &mut context.thread_local.selector_flags;