style: Remove (mostly) unused has_current_styles.

MozReview-Commit-ID: DV9HfvbUjBY

components/style/dom.rs

@@ -470,15 +470,6 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
     /// Flags this element as having handled already its snapshot.
     unsafe fn set_handled_snapshot(&self);
 
-    /// Returns whether the element's styles are up-to-date.
-    fn has_current_styles(&self, data: &ElementData) -> bool {
-        if self.has_snapshot() && !self.handled_snapshot() {
-            return false;
-        }
-
-        data.has_styles() && !data.has_invalidations()
-    }
-
     /// Returns whether the element's styles are up-to-date for |traversal_flags|.
     fn has_current_styles_for_traversal(
         &self,

components/style/style_resolver.rs

@@ -52,17 +52,7 @@ where
 {
     let parent_el = element.inheritance_parent();
     let parent_data = parent_el.as_ref().and_then(|e| e.borrow_data());
-    let parent_style = parent_data.as_ref().map(|d| {
+    let parent_style = parent_data.as_ref().map(|d| d.styles.primary());
-        // Sometimes Gecko eagerly styles things without processing
-        // pending restyles first. In general we'd like to avoid this,
-        // but there can be good reasons (for example, needing to
-        // construct a frame for some small piece of newly-added
-        // content in order to do something specific with that frame,
-        // but not wanting to flush all of layout).
-        debug_assert!(cfg!(feature = "gecko") ||
-                      parent_el.unwrap().has_current_styles(d));
-        d.styles.primary()
-    });
 
     let mut layout_parent_el = parent_el.clone();
     let layout_parent_data;

components/style/traversal.rs

@@ -376,7 +376,7 @@ pub trait DomTraversal<E: TElement> : Sync {
     ) -> bool {
         // See the comment on `cascade_node` for why we allow this on Gecko.
         debug_assert!(cfg!(feature = "gecko") ||
-                      parent.has_current_styles(parent_data));
+                      parent.has_current_styles_for_traversal(parent_data, context.shared.traversal_flags));
 
         // If the parent computed display:none, we don't style the subtree.
         if parent_data.styles.is_display_none() {