Auto merge of #17541 - heycam:is-needed, r=emilio

style: Make GeckoElement::traversal_children faster.

From https://bugzilla.mozilla.org/show_bug.cgi?id=1372061.

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---
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components/script/layout_wrapper.rs

@@ -187,12 +187,6 @@ impl<'ln> TNode for ServoLayoutNode<'ln> {
         self.children()
     }
 
-    fn children_and_traversal_children_might_differ(&self) -> bool {
-        // Servo doesn't have to worry about nodes being rearranged in the
-        // flattened tree like Gecko does (for XBL and Shadow DOM).  Yet.
-        false
-    }
-
     fn opaque(&self) -> OpaqueNode {
         unsafe { self.get_jsmanaged().opaque() }
     }

components/style/dom.rs

@@ -127,10 +127,6 @@ pub trait TNode : Sized + Copy + Clone + Debug + NodeInfo {
     /// Get this node's children from the perspective of a restyle traversal.
     fn traversal_children(&self) -> LayoutIterator<Self::ConcreteChildrenIterator>;
 
-    /// Returns whether `children()` and `traversal_children()` might return
-    /// iterators over different nodes.
-    fn children_and_traversal_children_might_differ(&self) -> bool;
-
     /// Converts self into an `OpaqueNode`.
     fn opaque(&self) -> OpaqueNode;
 

components/style/gecko/generated/atom_macro.rs

@@ -986,6 +986,8 @@ cfg_if! {
             pub static nsGkAtoms_handlers: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms4HARDE"]
             pub static nsGkAtoms_HARD: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms8haspopupE"]
+            pub static nsGkAtoms_haspopup: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms11hasSameNodeE"]
             pub static nsGkAtoms_hasSameNode: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms4hboxE"]
@@ -1562,6 +1564,8 @@ cfg_if! {
             pub static nsGkAtoms_onchargingtimechange: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms10oncheckingE"]
             pub static nsGkAtoms_onchecking: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms21onCheckboxStateChangeE"]
+            pub static nsGkAtoms_onCheckboxStateChange: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms7onclickE"]
             pub static nsGkAtoms_onclick: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms16onclirmodechangeE"]
@@ -1898,6 +1902,8 @@ cfg_if! {
             pub static nsGkAtoms_onptychange: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms18onradiostatechangeE"]
             pub static nsGkAtoms_onradiostatechange: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms18onRadioStateChangeE"]
+            pub static nsGkAtoms_onRadioStateChange: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms13onrdsdisabledE"]
             pub static nsGkAtoms_onrdsdisabled: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms12onrdsenabledE"]
@@ -4208,6 +4214,8 @@ cfg_if! {
             pub static nsGkAtoms_paintRequestTime: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms14pseudoPropertyE"]
             pub static nsGkAtoms_pseudoProperty: *mut nsIAtom;
+            #[link_name = "_ZN9nsGkAtoms17manualNACPropertyE"]
+            pub static nsGkAtoms_manualNACProperty: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms8JapaneseE"]
             pub static nsGkAtoms_Japanese: *mut nsIAtom;
             #[link_name = "_ZN9nsGkAtoms7ChineseE"]
@@ -6099,6 +6107,8 @@ cfg_if! {
             pub static nsGkAtoms_handlers: *mut nsIAtom;
             #[link_name = "?HARD@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_HARD: *mut nsIAtom;
+            #[link_name = "?haspopup@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_haspopup: *mut nsIAtom;
             #[link_name = "?hasSameNode@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_hasSameNode: *mut nsIAtom;
             #[link_name = "?hbox@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -6675,6 +6685,8 @@ cfg_if! {
             pub static nsGkAtoms_onchargingtimechange: *mut nsIAtom;
             #[link_name = "?onchecking@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_onchecking: *mut nsIAtom;
+            #[link_name = "?onCheckboxStateChange@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_onCheckboxStateChange: *mut nsIAtom;
             #[link_name = "?onclick@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_onclick: *mut nsIAtom;
             #[link_name = "?onclirmodechange@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -7011,6 +7023,8 @@ cfg_if! {
             pub static nsGkAtoms_onptychange: *mut nsIAtom;
             #[link_name = "?onradiostatechange@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_onradiostatechange: *mut nsIAtom;
+            #[link_name = "?onRadioStateChange@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_onRadioStateChange: *mut nsIAtom;
             #[link_name = "?onrdsdisabled@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_onrdsdisabled: *mut nsIAtom;
             #[link_name = "?onrdsenabled@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -9321,6 +9335,8 @@ cfg_if! {
             pub static nsGkAtoms_paintRequestTime: *mut nsIAtom;
             #[link_name = "?pseudoProperty@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_pseudoProperty: *mut nsIAtom;
+            #[link_name = "?manualNACProperty@nsGkAtoms@@2PEAVnsIAtom@@EA"]
+            pub static nsGkAtoms_manualNACProperty: *mut nsIAtom;
             #[link_name = "?Japanese@nsGkAtoms@@2PEAVnsIAtom@@EA"]
             pub static nsGkAtoms_Japanese: *mut nsIAtom;
             #[link_name = "?Chinese@nsGkAtoms@@2PEAVnsIAtom@@EA"]
@@ -11212,6 +11228,8 @@ cfg_if! {
             pub static nsGkAtoms_handlers: *mut nsIAtom;
             #[link_name = "\x01?HARD@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_HARD: *mut nsIAtom;
+            #[link_name = "\x01?haspopup@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_haspopup: *mut nsIAtom;
             #[link_name = "\x01?hasSameNode@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_hasSameNode: *mut nsIAtom;
             #[link_name = "\x01?hbox@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -11788,6 +11806,8 @@ cfg_if! {
             pub static nsGkAtoms_onchargingtimechange: *mut nsIAtom;
             #[link_name = "\x01?onchecking@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_onchecking: *mut nsIAtom;
+            #[link_name = "\x01?onCheckboxStateChange@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_onCheckboxStateChange: *mut nsIAtom;
             #[link_name = "\x01?onclick@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_onclick: *mut nsIAtom;
             #[link_name = "\x01?onclirmodechange@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -12124,6 +12144,8 @@ cfg_if! {
             pub static nsGkAtoms_onptychange: *mut nsIAtom;
             #[link_name = "\x01?onradiostatechange@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_onradiostatechange: *mut nsIAtom;
+            #[link_name = "\x01?onRadioStateChange@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_onRadioStateChange: *mut nsIAtom;
             #[link_name = "\x01?onrdsdisabled@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_onrdsdisabled: *mut nsIAtom;
             #[link_name = "\x01?onrdsenabled@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -14434,6 +14456,8 @@ cfg_if! {
             pub static nsGkAtoms_paintRequestTime: *mut nsIAtom;
             #[link_name = "\x01?pseudoProperty@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_pseudoProperty: *mut nsIAtom;
+            #[link_name = "\x01?manualNACProperty@nsGkAtoms@@2PAVnsIAtom@@A"]
+            pub static nsGkAtoms_manualNACProperty: *mut nsIAtom;
             #[link_name = "\x01?Japanese@nsGkAtoms@@2PAVnsIAtom@@A"]
             pub static nsGkAtoms_Japanese: *mut nsIAtom;
             #[link_name = "\x01?Chinese@nsGkAtoms@@2PAVnsIAtom@@A"]
@@ -16328,6 +16352,8 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_handlers as *mut _) } };
 ("HARD") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_HARD as *mut _) } };
+("haspopup") =>
+  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_haspopup as *mut _) } };
 ("has-same-node") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_hasSameNode as *mut _) } };
 ("hbox") =>
@@ -16904,6 +16930,8 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onchargingtimechange as *mut _) } };
 ("onchecking") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onchecking as *mut _) } };
+("onCheckboxStateChange") =>
+  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onCheckboxStateChange as *mut _) } };
 ("onclick") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onclick as *mut _) } };
 ("onclirmodechange") =>
@@ -17240,6 +17268,8 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onptychange as *mut _) } };
 ("onradiostatechange") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onradiostatechange as *mut _) } };
+("onRadioStateChange") =>
+  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onRadioStateChange as *mut _) } };
 ("onrdsdisabled") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_onrdsdisabled as *mut _) } };
 ("onrdsenabled") =>
@@ -19550,6 +19580,8 @@ macro_rules! atom {
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_paintRequestTime as *mut _) } };
 ("PseudoProperty") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_pseudoProperty as *mut _) } };
+("ManualNACProperty") =>
+  { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_manualNACProperty as *mut _) } };
 ("ja") =>
   { unsafe { $crate::string_cache::atom_macro::atom_from_static($crate::string_cache::atom_macro::nsGkAtoms_Japanese as *mut _) } };
 ("zh-CN") =>

components/style/gecko/generated/bindings.rs

@@ -29,6 +29,7 @@ use gecko_bindings::structs::RawServoStyleRule;
 use gecko_bindings::structs::RawGeckoPresContext;
 use gecko_bindings::structs::RawGeckoPresContextOwned;
 use gecko_bindings::structs::RawGeckoStyleAnimationList;
+use gecko_bindings::structs::RawGeckoStyleChildrenIteratorBorrowedMut;
 use gecko_bindings::structs::RawGeckoServoStyleRuleList;
 use gecko_bindings::structs::RawGeckoURLExtraData;
 use gecko_bindings::structs::RawGeckoXBLBinding;
@@ -227,14 +228,6 @@ pub type RawServoStyleSetBorrowedMut<'a> = &'a mut RawServoStyleSet;
 pub type RawServoStyleSetBorrowedMutOrNull<'a> = Option<&'a mut RawServoStyleSet>;
 enum RawServoStyleSetVoid { }
 pub struct RawServoStyleSet(RawServoStyleSetVoid);
-pub type StyleChildrenIteratorOwned = ::gecko_bindings::sugar::ownership::Owned<StyleChildrenIterator>;
-pub type StyleChildrenIteratorOwnedOrNull = ::gecko_bindings::sugar::ownership::OwnedOrNull<StyleChildrenIterator>;
-pub type StyleChildrenIteratorBorrowed<'a> = &'a StyleChildrenIterator;
-pub type StyleChildrenIteratorBorrowedOrNull<'a> = Option<&'a StyleChildrenIterator>;
-pub type StyleChildrenIteratorBorrowedMut<'a> = &'a mut StyleChildrenIterator;
-pub type StyleChildrenIteratorBorrowedMutOrNull<'a> = Option<&'a mut StyleChildrenIterator>;
-enum StyleChildrenIteratorVoid { }
-pub struct StyleChildrenIterator(StyleChildrenIteratorVoid);
 pub type ServoElementSnapshotOwned = ::gecko_bindings::sugar::ownership::Owned<ServoElementSnapshot>;
 pub type ServoElementSnapshotOwnedOrNull = ::gecko_bindings::sugar::ownership::OwnedOrNull<ServoElementSnapshot>;
 pub type ServoElementSnapshotBorrowed<'a> = &'a ServoElementSnapshot;
@@ -532,14 +525,18 @@ extern "C" {
                                                  *mut nsTArray<*mut nsIContent>);
 }
 extern "C" {
-    pub fn Gecko_MaybeCreateStyleChildrenIterator(node: RawGeckoNodeBorrowed)
+    pub fn Gecko_ConstructStyleChildrenIterator(aElement:
-     -> StyleChildrenIteratorOwnedOrNull;
+                                                    RawGeckoElementBorrowed,
+                                                aIterator:
+                                                    RawGeckoStyleChildrenIteratorBorrowedMut);
 }
 extern "C" {
-    pub fn Gecko_DropStyleChildrenIterator(it: StyleChildrenIteratorOwned);
+    pub fn Gecko_DestroyStyleChildrenIterator(aIterator:
+                                                  RawGeckoStyleChildrenIteratorBorrowedMut);
 }
 extern "C" {
-    pub fn Gecko_GetNextStyleChild(it: StyleChildrenIteratorBorrowedMut)
+    pub fn Gecko_GetNextStyleChild(it:
+                                       RawGeckoStyleChildrenIteratorBorrowedMut)
      -> RawGeckoNodeBorrowedOrNull;
 }
 extern "C" {

components/style/gecko/wrapper.rs

@@ -30,7 +30,7 @@ use gecko::global_style_data::GLOBAL_STYLE_DATA;
 use gecko::selector_parser::{SelectorImpl, NonTSPseudoClass, PseudoElement};
 use gecko::snapshot_helpers;
 use gecko_bindings::bindings;
-use gecko_bindings::bindings::{Gecko_DropStyleChildrenIterator, Gecko_MaybeCreateStyleChildrenIterator};
+use gecko_bindings::bindings::{Gecko_ConstructStyleChildrenIterator, Gecko_DestroyStyleChildrenIterator};
 use gecko_bindings::bindings::{Gecko_ElementState, Gecko_GetDocumentLWTheme};
 use gecko_bindings::bindings::{Gecko_GetLastChild, Gecko_GetNextStyleChild};
 use gecko_bindings::bindings::{Gecko_IsRootElement, Gecko_MatchesElement, Gecko_Namespace};
@@ -227,6 +227,21 @@ impl<'ln> GeckoNode<'ln> {
     fn contains_non_whitespace_content(&self) -> bool {
         unsafe { Gecko_IsSignificantChild(self.0, true, false) }
     }
+
+    #[inline]
+    fn may_have_anonymous_children(&self) -> bool {
+        self.get_bool_flag(nsINode_BooleanFlag::ElementMayHaveAnonymousChildren)
+    }
+
+    /// This logic is duplicated in Gecko's nsIContent::IsInAnonymousSubtree.
+    #[inline]
+    fn is_in_anonymous_subtree(&self) -> bool {
+        use gecko_bindings::structs::NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE;
+        use gecko_bindings::structs::NODE_IS_IN_SHADOW_TREE;
+        self.flags() & (NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE as u32) != 0 ||
+        ((self.flags() & (NODE_IS_IN_SHADOW_TREE as u32) == 0) &&
+         self.as_element().map_or(false, |e| e.has_xbl_binding_parent()))
+    }
 }
 
 impl<'ln> NodeInfo for GeckoNode<'ln> {
@@ -267,19 +282,23 @@ impl<'ln> TNode for GeckoNode<'ln> {
     }
 
     fn traversal_children(&self) -> LayoutIterator<GeckoChildrenIterator<'ln>> {
-        let maybe_iter = unsafe { Gecko_MaybeCreateStyleChildrenIterator(self.0) };
+        if let Some(element) = self.as_element() {
-        if let Some(iter) = maybe_iter.into_owned_opt() {
+            // This condition is similar to the check that
-            LayoutIterator(GeckoChildrenIterator::GeckoIterator(iter))
+            // StyleChildrenIterator::IsNeeded does, except that it might return
-        } else {
+            // true if we used to (but no longer) have anonymous content from
-            LayoutIterator(self.dom_children())
+            // ::before/::after, XBL bindings, or nsIAnonymousContentCreators.
+            if self.is_in_anonymous_subtree() ||
+               element.has_xbl_binding_with_content() ||
+               self.may_have_anonymous_children() {
+                unsafe {
+                    let mut iter: structs::StyleChildrenIterator = ::std::mem::zeroed();
+                    Gecko_ConstructStyleChildrenIterator(element.0, &mut iter);
+                    return LayoutIterator(GeckoChildrenIterator::GeckoIterator(iter));
+                }
+            }
         }
-    }
 
-    fn children_and_traversal_children_might_differ(&self) -> bool {
+        LayoutIterator(self.dom_children())
-        match self.as_element() {
-            Some(e) => e.xbl_binding_anonymous_content().is_some(),
-            None => false,
-        }
     }
 
     fn opaque(&self) -> OpaqueNode {
@@ -343,14 +362,14 @@ pub enum GeckoChildrenIterator<'a> {
     /// replaces it with the next sibling when requested.
     Current(Option<GeckoNode<'a>>),
     /// A Gecko-implemented iterator we need to drop appropriately.
-    GeckoIterator(bindings::StyleChildrenIteratorOwned),
+    GeckoIterator(structs::StyleChildrenIterator),
 }
 
 impl<'a> Drop for GeckoChildrenIterator<'a> {
     fn drop(&mut self) {
-        if let GeckoChildrenIterator::GeckoIterator(ref it) = *self {
+        if let GeckoChildrenIterator::GeckoIterator(ref mut it) = *self {
             unsafe {
-                Gecko_DropStyleChildrenIterator(ptr::read(it as *const _));
+                Gecko_DestroyStyleChildrenIterator(it);
             }
         }
     }
@@ -373,10 +392,11 @@ impl<'a> Iterator for GeckoChildrenIterator<'a> {
 }
 
 /// A Simple wrapper over a non-null Gecko `nsXBLBinding` pointer.
+#[derive(Clone, Copy)]
 pub struct GeckoXBLBinding<'lb>(pub &'lb RawGeckoXBLBinding);
 
 impl<'lb> GeckoXBLBinding<'lb> {
-    fn base_binding(&self) -> Option<GeckoXBLBinding> {
+    fn base_binding(&self) -> Option<Self> {
         unsafe { self.0.mNextBinding.mRawPtr.as_ref().map(GeckoXBLBinding) }
     }
 
@@ -388,6 +408,21 @@ impl<'lb> GeckoXBLBinding<'lb> {
         unsafe { bindings::Gecko_XBLBinding_InheritsStyle(self.0) }
     }
 
+    // This duplicates the logic in Gecko's
+    // nsBindingManager::GetBindingWithContent.
+    fn get_binding_with_content(&self) -> Option<Self> {
+        let mut binding = *self;
+        loop {
+            if !binding.anon_content().is_null() {
+                return Some(binding);
+            }
+            binding = match binding.base_binding() {
+                Some(b) => b,
+                None => return None,
+            };
+        }
+    }
+
     // Implements Gecko's nsXBLBinding::WalkRules().
     fn get_declarations_for<E, V>(&self,
                                   element: &E,
@@ -480,12 +515,71 @@ impl<'le> GeckoElement<'le> {
         unsafe { slots.as_ref() }
     }
 
+    #[inline]
     fn get_xbl_binding(&self) -> Option<GeckoXBLBinding> {
+        if self.flags() & (structs::NODE_MAY_BE_IN_BINDING_MNGR as u32) == 0 {
+            return None;
+        }
+
         unsafe { bindings::Gecko_GetXBLBinding(self.0).map(GeckoXBLBinding) }
     }
 
+    #[inline]
+    fn get_xbl_binding_with_content(&self) -> Option<GeckoXBLBinding> {
+        self.get_xbl_binding().and_then(|b| b.get_binding_with_content())
+    }
+
+    #[inline]
+    fn has_xbl_binding_with_content(&self) -> bool {
+        !self.get_xbl_binding_with_content().is_none()
+    }
+
+    /// This and has_xbl_binding_parent duplicate the logic in Gecko's virtual
+    /// nsINode::GetBindingParent function, which only has two implementations:
+    /// one for XUL elements, and one for other elements.  We just hard code in
+    /// our knowledge of those two implementations here.
     fn get_xbl_binding_parent(&self) -> Option<Self> {
-        unsafe { bindings::Gecko_GetBindingParent(self.0).map(GeckoElement) }
+        if self.is_xul_element() {
+            // FIXME(heycam): Having trouble with bindgen on nsXULElement,
+            // where the binding parent is stored in a member variable
+            // rather than in slots.  So just get it through FFI for now.
+            unsafe { bindings::Gecko_GetBindingParent(self.0).map(GeckoElement) }
+        } else {
+            let binding_parent =
+                unsafe { self.get_non_xul_xbl_binding_parent_raw_content().as_ref() }
+                    .map(GeckoNode::from_content)
+                    .and_then(|n| n.as_element());
+            debug_assert!(binding_parent ==
+                            unsafe { bindings::Gecko_GetBindingParent(self.0).map(GeckoElement) });
+            binding_parent
+        }
+    }
+
+    fn get_non_xul_xbl_binding_parent_raw_content(&self) -> *mut nsIContent {
+        debug_assert!(!self.is_xul_element());
+        match self.get_dom_slots() {
+            Some(slots) => unsafe { *slots.__bindgen_anon_1.mBindingParent.as_ref() },
+            None => ptr::null_mut(),
+        }
+    }
+
+    fn has_xbl_binding_parent(&self) -> bool {
+        if self.is_xul_element() {
+            // FIXME(heycam): Having trouble with bindgen on nsXULElement,
+            // where the binding parent is stored in a member variable
+            // rather than in slots.  So just get it through FFI for now.
+            unsafe { bindings::Gecko_GetBindingParent(self.0).is_some() }
+        } else {
+            !self.get_non_xul_xbl_binding_parent_raw_content().is_null()
+        }
+    }
+
+    fn namespace_id(&self) -> i32 {
+        self.as_node().node_info().mInner.mNamespaceID
+    }
+
+    fn is_xul_element(&self) -> bool {
+        self.namespace_id() == (structs::root::kNameSpaceID_XUL as i32)
     }
 
     /// Clear the element data for a given element.
@@ -1061,16 +1155,9 @@ impl<'le> TElement for GeckoElement<'le> {
     }
 
     fn xbl_binding_anonymous_content(&self) -> Option<GeckoNode<'le>> {
-        if self.flags() & (structs::NODE_MAY_BE_IN_BINDING_MNGR as u32) == 0 {
+        self.get_xbl_binding_with_content()
-            return None;
+            .map(|b| unsafe { b.anon_content().as_ref() }.unwrap())
-        }
+            .map(GeckoNode::from_content)
-
-        let anon_content = match self.get_xbl_binding() {
-            Some(binding) => binding.anon_content(),
-            None => return None,
-        };
-
-        unsafe { anon_content.as_ref().map(GeckoNode::from_content) }
     }
 
     fn get_css_transitions_info(&self)