Move selector matching tests and testing helpers into a #[cfg(test)] module.

src/components/style/selector_matching.rs

@@ -710,6 +710,8 @@ fn match_attribute<E:TElement,
 }
 
 
+#[cfg(test)]
+mod tests {
     /// Helper method to get some Rules from selector strings.
     /// Each sublist of the result contains the Rules for one StyleRule.
     fn get_mock_rules(css_selectors: &[&str]) -> ~[~[Rule]] {
@@ -772,4 +774,4 @@ fn test_insert(){
         assert_eq!(0, selector_map.class_hash.find(&~"intro").unwrap()[0].index);
         assert!(selector_map.class_hash.find(&~"foo").is_none());
     }
-
+}