selectors: Remove unused visit_simple_selectors.

components/selectors/parser.rs

@@ -185,10 +185,6 @@ impl<Impl: SelectorImpl> SelectorMethods for SimpleSelector<Impl> {
     {
         use self::SimpleSelector::*;
 
-        if !visitor.visit_simple_selector(self) {
-            return false;
-        }
-
         match *self {
             Negation(ref negated) => {
                 for selector in negated {

components/selectors/visitor.rs

@@ -6,7 +6,7 @@
 
 #![deny(missing_docs)]
 
-use parser::{AttrSelector, Combinator, ComplexSelector, SelectorImpl, SimpleSelector};
+use parser::{AttrSelector, Combinator, ComplexSelector, SelectorImpl};
 use std::sync::Arc;
 
 /// A trait to visit selector properties.
@@ -34,9 +34,4 @@ pub trait SelectorVisitor {
                               -> bool {
         true
     }
-
-    /// Visits a simple selector.
-    fn visit_simple_selector(&mut self, _: &SimpleSelector<Self::Impl>) -> bool {
-        true
-    }
 }