style: Clean up some stylist code and make it slightly more efficient.

components/style/stylist.rs

@@ -549,7 +549,7 @@ impl Stylist {
         if *local_name == local_name!("style") {
             self.style_attribute_dependency
         } else {
-            self.attribute_dependencies.might_contain(local_name)
+            self.attribute_dependencies.might_contain_hash(local_name.get_hash())
         }
     }
 
@@ -1169,7 +1169,7 @@ impl Stylist {
     /// of our rule maps.
     #[inline]
     pub fn may_have_rules_for_id(&self, id: &Atom) -> bool {
-        self.mapped_ids.might_contain(id)
+        self.mapped_ids.might_contain_hash(id.get_hash())
     }
 
     /// Return whether the device is dirty, that is, whether the screen size or
@@ -1304,16 +1304,11 @@ impl<'a> SelectorVisitor for AttributeAndStateDependencyVisitor<'a> {
     fn visit_attribute_selector(&mut self, _ns: &NamespaceConstraint<&Namespace>,
                                 name: &LocalName, lower_name: &LocalName)
                                 -> bool {
-        #[cfg(feature = "servo")]
-        let style_lower_name = local_name!("style");
-        #[cfg(feature = "gecko")]
-        let style_lower_name = atom!("style");
-
-        if *lower_name == style_lower_name {
+        if *lower_name == local_name!("style") {
             *self.style_attribute_dependency = true;
         } else {
-            self.attribute_dependencies.insert(&name);
-            self.attribute_dependencies.insert(&lower_name);
+            self.attribute_dependencies.insert_hash(name.get_hash());
+            self.attribute_dependencies.insert_hash(lower_name.get_hash());
         }
         true
     }
@@ -1337,7 +1332,7 @@ impl<'a> SelectorVisitor for MappedIdVisitor<'a> {
     /// We just want to insert all the ids we find into mapped_ids.
     fn visit_simple_selector(&mut self, s: &Component<SelectorImpl>) -> bool {
         if let Component::ID(ref id) = *s {
-            self.mapped_ids.insert(id);
+            self.mapped_ids.insert_hash(id.get_hash());
         }
         true
     }