Transitively deparent on removal

Chrome and Firefox do this already, probably a spec oversight

components/script/dom/csskeyframesrule.rs

@@ -55,6 +55,7 @@ impl CSSKeyframesRule {
 }
 
 impl CSSKeyframesRuleMethods for CSSKeyframesRule {
+    // https://drafts.csswg.org/css-animations/#dom-csskeyframesrule-cssrules
     fn CssRules(&self) -> Root<CSSRuleList> {
         self.rulelist()
     }
@@ -69,4 +70,8 @@ impl SpecificCSSRule for CSSKeyframesRule {
     fn get_css(&self) -> DOMString {
         self.keyframesrule.read().to_css_string().into()
     }
+
+    fn deparent_children(&self) {
+        self.rulelist.get().map(|list| list.deparent_all());
+    }
 }

components/script/dom/cssrule.rs

@@ -9,8 +9,8 @@ use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
 use dom::cssfontfacerule::CSSFontFaceRule;
-use dom::csskeyframesrule::CSSKeyframesRule;
 use dom::csskeyframerule::CSSKeyframeRule;
+use dom::csskeyframesrule::CSSKeyframesRule;
 use dom::cssmediarule::CSSMediaRule;
 use dom::cssnamespacerule::CSSNamespaceRule;
 use dom::cssstylerule::CSSStyleRule;
@@ -78,10 +78,18 @@ impl CSSRule {
     }
 
     /// Sets owner sheet/rule to null
-    pub fn disown(&self) {
+    pub fn detach(&self) {
-        self.parent.set(None);
+        self.deparent();
         // should set parent rule to None when we add parent rule support
-        // Should we disown children as well? (https://github.com/w3c/csswg-drafts/issues/722)
+    }
+
+    /// Sets owner sheet to null (and does the same for all children)
+    pub fn deparent(&self) {
+        self.parent.set(None);
+        // https://github.com/w3c/csswg-drafts/issues/722
+        // Spec doesn't ask us to do this, but it makes sense
+        // and browsers implement this behavior
+        self.as_specific().deparent_children();
     }
 }
 
@@ -110,4 +118,8 @@ impl CSSRuleMethods for CSSRule {
 pub trait SpecificCSSRule {
     fn ty(&self) -> u16;
     fn get_css(&self) -> DOMString;
+    /// Remove CSSStyleSheet parent from all transitive children
+    fn deparent_children(&self) {
+        // most CSSRules do nothing here
+    }
 }

components/script/dom/cssrulelist.rs

@@ -9,8 +9,8 @@ use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::reflector::{Reflectable, Reflector, reflect_dom_object};
-use dom::cssrule::CSSRule;
 use dom::csskeyframerule::CSSKeyframeRule;
+use dom::cssrule::CSSRule;
 use dom::cssstylesheet::CSSStyleSheet;
 use dom::window::Window;
 use parking_lot::RwLock;
@@ -166,10 +166,17 @@ impl CSSRuleList {
 
         let mut dom_rules = self.dom_rules.borrow_mut();
         css_rules.0.write().remove(index);
-        dom_rules[index].get().map(|r| r.disown());
+        dom_rules[index].get().map(|r| r.detach());
         dom_rules.remove(index);
         Ok(())
     }
+
+    // Remove parent stylesheets from all children
+    pub fn deparent_all(&self) {
+        for rule in self.dom_rules.borrow().iter() {
+            rule.get().map(|r| Root::upcast(r).deparent());
+        }
+    }
 }
 
 impl CSSRuleListMethods for CSSRuleList {

components/script/dom/mod.rs

@@ -244,8 +244,8 @@ pub mod crypto;
 pub mod css;
 pub mod cssfontfacerule;
 pub mod cssgroupingrule;
-pub mod csskeyframesrule;
 pub mod csskeyframerule;
+pub mod csskeyframesrule;
 pub mod cssmediarule;
 pub mod cssnamespacerule;
 pub mod cssrule;