Introduce VirtualMethods::presentational_hints.

components/script/dom/attr.rs

@@ -262,6 +262,7 @@ impl<'a> AttrHelpers<'a> for &'a Attr {
         *self.value.borrow_mut() = value;
 
         if namespace_is_null {
+            *self.presentational_hints.borrow_mut() = vtable_for(&node).presentational_hints(self);
             vtable_for(&node).after_set_attr(self)
         }
     }

components/script/dom/virtualmethods.rs

@@ -37,6 +37,7 @@ use dom::event::Event;
 use dom::htmlelement::HTMLElementTypeId;
 use dom::node::{Node, NodeHelpers, NodeTypeId, CloneChildrenFlag};
 
+use style::properties::PropertyDeclaration;
 use util::str::DOMString;
 
 use string_cache::Atom;
@@ -81,6 +82,14 @@ pub trait VirtualMethods {
         }
     }
 
+    /// ...
+    fn presentational_hints(&self, attribute: JSRef<Attr>) -> Vec<PropertyDeclaration> {
+        match self.super_type() {
+            Some(ref s) => s.presentational_hints(attribute),
+            _ => Vec::new(),
+        }
+    }
+
     /// Called when a Node is appended to a tree, where 'tree_in_doc' indicates
     /// whether the tree is part of a Document.
     fn bind_to_tree(&self, tree_in_doc: bool) {