Replace RwLock<CssRules> with Locked<CssRules>

components/script/dom/cssstylesheet.rs

@@ -16,6 +16,7 @@ use dom::window::Window;
 use dom_struct::dom_struct;
 use std::cell::Cell;
 use std::sync::Arc;
+use style::shared_lock::SharedRwLock;
 use style::stylesheets::Stylesheet as StyleStyleSheet;
 
 #[dom_struct]
@@ -72,6 +73,10 @@ impl CSSStyleSheet {
         }
     }
 
+    pub fn shared_lock(&self) -> &SharedRwLock {
+        &self.style_stylesheet.shared_lock
+    }
+
     pub fn style_stylesheet(&self) -> &StyleStyleSheet {
         &self.style_stylesheet
     }