Make parent stylesheet optional for CSSRules

1 files changed, 12 insertions, 7 deletions

diff --git a/components/script/dom/cssrulelist.rs b/components/script/dom/cssrulelist.rs
index 902f3c8a189..ebdea9f2ca0 100644
--- a/components/script/dom/cssrulelist.rs
+++ b/components/script/dom/cssrulelist.rs
@@ -24,7 +24,7 @@ no_jsmanaged_fields!(RulesSource);
 #[dom_struct]
 pub struct CSSRuleList {
     reflector_: Reflector,
-    sheet: JS<CSSStyleSheet>,
+    sheet: MutNullableHeap<JS<CSSStyleSheet>>,
     #[ignore_heap_size_of = "Arc"]
     rules: RulesSource,
     dom_rules: DOMRefCell<Vec<MutNullableHeap<JS<CSSRule>>>>
@@ -37,7 +37,7 @@ pub enum RulesSource {
 
 impl CSSRuleList {
     #[allow(unrooted_must_root)]
-    pub fn new_inherited(sheet: &CSSStyleSheet, rules: RulesSource) -> CSSRuleList {
+    pub fn new_inherited(sheet: Option<&CSSStyleSheet>, rules: RulesSource) -> CSSRuleList {
         let dom_rules = match rules {
             RulesSource::Rules(ref rules) => {
                 rules.0.read().iter().map(|_| MutNullableHeap::new(None)).collect()
@@ -49,14 +49,15 @@ impl CSSRuleList {
 
         CSSRuleList {
             reflector_: Reflector::new(),
-            sheet: JS::from_ref(sheet),
+            sheet: MutNullableHeap::new(sheet),
             rules: rules,
             dom_rules: DOMRefCell::new(dom_rules),
         }
     }
 
     #[allow(unrooted_must_root)]
-    pub fn new(window: &Window, sheet: &CSSStyleSheet, rules: RulesSource) -> Root<CSSRuleList> {
+    pub fn new(window: &Window, sheet: Option<&CSSStyleSheet>,
+               rules: RulesSource) -> Root<CSSRuleList> {
         reflect_dom_object(box CSSRuleList::new_inherited(sheet, rules),
                            window,
                            CSSRuleListBinding::Wrap)
@@ -132,7 +133,9 @@ impl CSSRuleList {
         };
 
         insert(&mut css_rules.0.write(), index, new_rule.clone());
-        let dom_rule = CSSRule::new_specific(&window, &self.sheet, new_rule);
+        let sheet = self.sheet.get();
+        let sheet = sheet.as_ref().map(|sheet| &**sheet);
+        let dom_rule = CSSRule::new_specific(&window, sheet, new_rule);
         insert(&mut self.dom_rules.borrow_mut(),
                index, MutNullableHeap::new(Some(&*dom_rule)));
         Ok((idx))
@@ -174,15 +177,17 @@ impl CSSRuleListMethods for CSSRuleList {
     fn Item(&self, idx: u32) -> Option<Root<CSSRule>> {
         self.dom_rules.borrow().get(idx as usize).map(|rule| {
             rule.or_init(|| {
+                let sheet = self.sheet.get();
+                let sheet = sheet.as_ref().map(|sheet| &**sheet);
                 match self.rules {
                     RulesSource::Rules(ref rules) => {
                         CSSRule::new_specific(self.global().as_window(),
-                                             &self.sheet,
+                                             sheet,
                                              rules.0.read()[idx as usize].clone())
                     }
                     RulesSource::Keyframes(ref rules) => {
                         Root::upcast(CSSKeyframeRule::new(self.global().as_window(),
-                                                          &self.sheet,
+                                                          sheet,
                                                           rules.read()
                                                                 .keyframes[idx as usize]
                                                                 .clone()))