--- a/dom/xbl/nsXBLBinding.cpp
+++ b/dom/xbl/nsXBLBinding.cpp
@@ -866,16 +866,22 @@ nsXBLBinding::WalkRules(nsIStyleRuleProc
   if (mNextBinding)
     mNextBinding->WalkRules(aFunc, aData);
 
   nsIStyleRuleProcessor *rules = mPrototypeBinding->GetRuleProcessor();
   if (rules)
     (*aFunc)(rules, aData);
 }
 
+const ServoStyleSet*
+nsXBLBinding::GetServoStyleSet() const
+{
+  return mPrototypeBinding->GetServoStyleSet();
+}
+
 // Internal helper methods ////////////////////////////////////////////////////////////////
 
 // Get or create a WeakMap object on a given XBL-hosting global.
 //
 // The scheme is as follows. XBL-hosting globals (either privileged content
 // Windows or XBL scopes) get two lazily-defined WeakMap properties. Each
 // WeakMap is keyed by the grand-proto - i.e. the original prototype of the
 // content before it was bound, and the prototype of the class object that we

--- a/dom/xbl/nsXBLBinding.h
+++ b/dom/xbl/nsXBLBinding.h
@@ -2,16 +2,17 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef nsXBLBinding_h_
 #define nsXBLBinding_h_
 
+#include "mozilla/ServoBindings.h"
 #include "nsXBLService.h"
 #include "nsCOMPtr.h"
 #include "nsINodeList.h"
 #include "nsIStyleRuleProcessor.h"
 #include "nsClassHashtable.h"
 #include "nsTArray.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsISupportsImpl.h"
@@ -124,16 +125,18 @@ public:
 
   void AttributeChanged(nsIAtom* aAttribute, int32_t aNameSpaceID,
                         bool aRemoveFlag, bool aNotify);
 
   void ChangeDocument(nsIDocument* aOldDocument, nsIDocument* aNewDocument);
 
   void WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc, void* aData);
 
+  const mozilla::ServoStyleSet* GetServoStyleSet() const;
+
   static nsresult DoInitJSClass(JSContext *cx, JS::Handle<JSObject*> obj,
                                 const nsAFlatString& aClassName,
                                 nsXBLPrototypeBinding* aProtoBinding,
                                 JS::MutableHandle<JSObject*> aClassObject,
                                 bool* aNew);
 
   bool AllowScripts();
 

--- a/dom/xbl/nsXBLPrototypeBinding.cpp
+++ b/dom/xbl/nsXBLPrototypeBinding.cpp
@@ -564,16 +564,22 @@ nsXBLPrototypeBinding::GetRuleProcessor(
 {
   if (mResources) {
     return mResources->GetRuleProcessor();
   }
 
   return nullptr;
 }
 
+const ServoStyleSet*
+nsXBLPrototypeBinding::GetServoStyleSet() const
+{
+  return mResources ? mResources->GetServoStyleSet() : nullptr;
+}
+
 void
 nsXBLPrototypeBinding::EnsureAttributeTable()
 {
   if (!mAttributeTable) {
     mAttributeTable =
         new nsClassHashtable<nsUint32HashKey, InnerAttributeTable>(2);
   }
 }

--- a/dom/xbl/nsXBLPrototypeBinding.h
+++ b/dom/xbl/nsXBLPrototypeBinding.h
@@ -126,16 +126,17 @@ public:
   void RemoveStyleSheet(mozilla::StyleSheet* aSheet);
   void InsertStyleSheetAt(size_t aIndex, mozilla::StyleSheet* aSheet);
   mozilla::StyleSheet* StyleSheetAt(size_t aIndex) const;
   size_t SheetCount() const;
   bool HasStyleSheets() const;
   void AppendStyleSheetsTo(nsTArray<mozilla::StyleSheet*>& aResult) const;
 
   nsIStyleRuleProcessor* GetRuleProcessor();
+  const mozilla::ServoStyleSet* GetServoStyleSet() const;
 
   nsresult FlushSkinSheets();
 
   nsIAtom* GetBaseTag(int32_t* aNamespaceID);
   void SetBaseTag(int32_t aNamespaceID, nsIAtom* aTag);
 
   bool ImplementsInterface(REFNSIID aIID) const;
 

--- a/dom/xbl/nsXBLPrototypeResources.h
+++ b/dom/xbl/nsXBLPrototypeResources.h
@@ -2,16 +2,17 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef nsXBLPrototypeResources_h__
 #define nsXBLPrototypeResources_h__
 
+#include "mozilla/ServoBindings.h"
 #include "mozilla/StyleSheet.h"
 #include "nsICSSLoaderObserver.h"
 
 class nsCSSRuleProcessor;
 class nsIAtom;
 class nsIContent;
 class nsXBLPrototypeBinding;
 class nsXBLResourceLoader;
@@ -59,16 +60,18 @@ public:
 
   nsCSSRuleProcessor* GetRuleProcessor() const { return mRuleProcessor; }
 
   // Updates the ServoStyleSet object that holds the result of cascading the
   // sheets in mStyleSheetList. Equivalent to GatherRuleProcessor(), but for
   // the Servo style backend.
   void ComputeServoStyleSet(nsPresContext* aPresContext);
 
+  const mozilla::ServoStyleSet* GetServoStyleSet() const { return mServoStyleSet.get(); }
+
 private:
   // A loader object. Exists only long enough to load resources, and then it dies.
   RefPtr<nsXBLResourceLoader> mLoader;
 
   // A list of loaded stylesheets for this binding.
   nsTArray<RefPtr<mozilla::StyleSheet>> mStyleSheetList;
 
   // The list of stylesheets converted to a rule processor.

--- a/layout/style/ServoBindingTypes.h
+++ b/layout/style/ServoBindingTypes.h
@@ -42,24 +42,26 @@ enum class MatrixTransformOperator: uint
 
 class nsCSSPropertyIDSet;
 class nsCSSValue;
 struct nsFontFaceRuleContainer;
 class nsIDocument;
 class nsINode;
 class nsPresContext;
 struct nsTimingFunction;
+class nsXBLBinding;
 
 using mozilla::dom::StyleChildrenIterator;
 using mozilla::ServoElementSnapshot;
 
 typedef nsINode RawGeckoNode;
 typedef mozilla::dom::Element RawGeckoElement;
 typedef nsIDocument RawGeckoDocument;
 typedef nsPresContext RawGeckoPresContext;
+typedef nsXBLBinding RawGeckoXBLBinding;
 typedef mozilla::URLExtraData RawGeckoURLExtraData;
 typedef nsTArray<mozilla::Keyframe> RawGeckoKeyframeList;
 typedef nsTArray<mozilla::ComputedKeyframeValues> RawGeckoComputedKeyframeValuesList;
 typedef nsTArray<mozilla::PropertyStyleAnimationValuePair> RawGeckoAnimationValueList;
 typedef nsStyleAutoArray<mozilla::StyleAnimation> RawGeckoStyleAnimationList;
 typedef nsTArray<nsFontFaceRuleContainer> RawGeckoFontFaceRuleList;
 typedef mozilla::AnimationPropertySegment RawGeckoAnimationPropertySegment;
 typedef mozilla::ComputedTiming RawGeckoComputedTiming;
@@ -109,32 +111,35 @@ typedef mozilla::gfx::Float RawGeckoGfxM
   DECL_NULLABLE_BORROWED_REF_TYPE_FOR(type_)       \
   DECL_NULLABLE_BORROWED_MUT_REF_TYPE_FOR(type_)
 
 // This is a reference to a reference of RawServoDeclarationBlock, which
 // corresponds to Option<&Arc<RawServoDeclarationBlock>> in Servo side.
 DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawServoDeclarationBlockStrong)
 
 DECL_OWNED_REF_TYPE_FOR(RawServoStyleSet)
+DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawServoStyleSet)
 DECL_NULLABLE_OWNED_REF_TYPE_FOR(StyleChildrenIterator)
 DECL_OWNED_REF_TYPE_FOR(StyleChildrenIterator)
 DECL_OWNED_REF_TYPE_FOR(ServoElementSnapshot)
 DECL_OWNED_REF_TYPE_FOR(RawServoAnimationValueMap)
 
 // We don't use BorrowedMut because the nodes may alias
 // Servo itself doesn't directly read or mutate these;
 // it only asks Gecko to do so. In case we wish to in
 // the future, we should ensure that things being mutated
 // are protected from noalias violations by a cell type
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoNode)
 DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawGeckoNode)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoElement)
 DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawGeckoElement)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoDocument)
 DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawGeckoDocument)
+DECL_BORROWED_REF_TYPE_FOR(RawGeckoXBLBinding)
+DECL_NULLABLE_BORROWED_REF_TYPE_FOR(RawGeckoXBLBinding)
 DECL_BORROWED_MUT_REF_TYPE_FOR(StyleChildrenIterator)
 DECL_BORROWED_MUT_REF_TYPE_FOR(ServoElementSnapshot)
 DECL_BORROWED_REF_TYPE_FOR(nsCSSValue)
 DECL_BORROWED_MUT_REF_TYPE_FOR(nsCSSValue)
 DECL_OWNED_REF_TYPE_FOR(RawGeckoPresContext)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoPresContext)
 DECL_BORROWED_MUT_REF_TYPE_FOR(RawGeckoAnimationValueList)
 DECL_BORROWED_MUT_REF_TYPE_FOR(RawGeckoKeyframeList)
@@ -144,16 +149,17 @@ DECL_BORROWED_REF_TYPE_FOR(RawGeckoStyle
 DECL_BORROWED_MUT_REF_TYPE_FOR(nsTimingFunction)
 DECL_BORROWED_REF_TYPE_FOR(nsTimingFunction)
 DECL_BORROWED_MUT_REF_TYPE_FOR(RawGeckoFontFaceRuleList)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoAnimationPropertySegment)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoComputedTiming)
 DECL_BORROWED_MUT_REF_TYPE_FOR(RawGeckoServoStyleRuleList)
 DECL_BORROWED_MUT_REF_TYPE_FOR(nsCSSPropertyIDSet)
 DECL_BORROWED_REF_TYPE_FOR(RawGeckoCSSPropertyIDList)
+DECL_BORROWED_REF_TYPE_FOR(nsXBLBinding)
 
 #undef DECL_ARC_REF_TYPE_FOR
 #undef DECL_OWNED_REF_TYPE_FOR
 #undef DECL_NULLABLE_OWNED_REF_TYPE_FOR
 #undef DECL_BORROWED_REF_TYPE_FOR
 #undef DECL_NULLABLE_BORROWED_REF_TYPE_FOR
 #undef DECL_BORROWED_MUT_REF_TYPE_FOR
 #undef DECL_NULLABLE_BORROWED_MUT_REF_TYPE_FOR

--- a/layout/style/ServoBindings.cpp
+++ b/layout/style/ServoBindings.cpp
@@ -2182,16 +2182,42 @@ Gecko_GetBaseSize(nsIAtom* aLanguage)
 
   prefs.Initialize(langGroupAtom);
   FontSizePrefs sizes;
   sizes.CopyFrom(prefs);
 
   return sizes;
 }
 
+RawGeckoElementBorrowedOrNull
+Gecko_GetBindingParent(RawGeckoElementBorrowed aElement)
+{
+  nsIContent* parent = aElement->GetBindingParent();
+  return parent ? parent->AsElement() : nullptr;
+}
+
+RawGeckoXBLBindingBorrowedOrNull
+Gecko_GetXBLBinding(RawGeckoElementBorrowed aElement)
+{
+  return aElement->GetXBLBinding();
+}
+
+RawServoStyleSetBorrowedOrNull
+Gecko_XBLBinding_GetRawServoStyleSet(RawGeckoXBLBindingBorrowed aXBLBinding)
+{
+  const ServoStyleSet* set = aXBLBinding->GetServoStyleSet();
+  return set ? set->RawSet() : nullptr;
+}
+
+bool
+Gecko_XBLBinding_InheritsStyle(RawGeckoXBLBindingBorrowed aXBLBinding)
+{
+  return aXBLBinding->InheritsStyle();
+}
+
 void
 InitializeServo()
 {
   URLExtraData::InitDummy();
   Servo_Initialize(URLExtraData::Dummy());
 
   sServoFontMetricsLock = new Mutex("Gecko_GetFontMetrics");
   sServoLangFontPrefsLock = new RWLock("nsPresContext::GetDefaultFont");

--- a/layout/style/ServoBindings.h
+++ b/layout/style/ServoBindings.h
@@ -59,16 +59,17 @@ class nsCSSCounterStyleRule;
 class nsCSSFontFaceRule;
 struct nsMediaFeature;
 struct nsStyleList;
 struct nsStyleImage;
 struct nsStyleGradientStop;
 class nsStyleGradient;
 class nsStyleCoord;
 struct nsStyleDisplay;
+class nsXBLBinding;
 
 #define NS_DECL_THREADSAFE_FFI_REFCOUNTING(class_, name_)                     \
   void Gecko_AddRef##name_##ArbitraryThread(class_* aPtr);                    \
   void Gecko_Release##name_##ArbitraryThread(class_* aPtr);
 #define NS_IMPL_THREADSAFE_FFI_REFCOUNTING(class_, name_)                     \
   static_assert(class_::HasThreadSafeRefCnt::value,                           \
                 "NS_DECL_THREADSAFE_FFI_REFCOUNTING can only be used with "   \
                 "classes that have thread-safe refcounting");                 \
@@ -522,16 +523,22 @@ void Gecko_nsStyleFont_FixupNoneGeneric(
                                         RawGeckoPresContextBorrowed pres_context);
 void Gecko_nsStyleFont_PrefillDefaultForGeneric(nsStyleFont* font,
                                                 RawGeckoPresContextBorrowed pres_context,
                                                 uint8_t generic_id);
 void Gecko_nsStyleFont_FixupMinFontSize(nsStyleFont* font,
                                         RawGeckoPresContextBorrowed pres_context);
 FontSizePrefs Gecko_GetBaseSize(nsIAtom* lang);
 
+// XBL related functions.
+RawGeckoElementBorrowedOrNull Gecko_GetBindingParent(RawGeckoElementBorrowed aElement);
+RawGeckoXBLBindingBorrowedOrNull Gecko_GetXBLBinding(RawGeckoElementBorrowed aElement);
+RawServoStyleSetBorrowedOrNull Gecko_XBLBinding_GetRawServoStyleSet(RawGeckoXBLBindingBorrowed aXBLBinding);
+bool Gecko_XBLBinding_InheritsStyle(RawGeckoXBLBindingBorrowed aXBLBinding);
+
 struct GeckoFontMetrics
 {
   nscoord mChSize;
   nscoord mXSize;
 };
 
 GeckoFontMetrics Gecko_GetFontMetrics(RawGeckoPresContextBorrowed pres_context,
                                       bool is_vertical,

--- a/layout/style/ServoBindings.toml
+++ b/layout/style/ServoBindings.toml
@@ -59,16 +59,17 @@ headers = [
     "mozilla/dom/Element.h",
     "mozilla/dom/NameSpaceConstants.h",
     "mozilla/LookAndFeel.h",
     "mozilla/ServoBindings.h",
     "nsCSSCounterStyleRule.h",
     "nsCSSFontFaceRule.h",
     "nsMediaFeatures.h",
     "nsMediaList.h",
+    "nsXBLBinding.h",
 ]
 raw-lines = [
     # FIXME(emilio): Incrementally remove these "pub use"s. Probably
     # mozilla::css and mozilla::dom are easier.
     "pub use self::root::*;",
     "pub use self::root::mozilla::*;",
     "pub use self::root::mozilla::css::*;",
     "pub use self::root::mozilla::dom::*;",
@@ -341,16 +342,17 @@ structs-types = [
     "RawServoAnimationValue",
     "RawServoDeclarationBlock",
     "RawServoStyleRule",
     "RawGeckoPresContext",
     "RawGeckoPresContextOwned",
     "RawGeckoStyleAnimationList",
     "RawGeckoServoStyleRuleList",
     "RawGeckoURLExtraData",
+    "RawGeckoXBLBinding",
     "RefPtr",
     "CSSPseudoClassType",
     "CSSPseudoElementType",
     "TraversalRestyleBehavior",
     "TraversalRootBehavior",
     "ComputedTimingFunction_BeforeFlag",
     "CounterStylePtr",
     "FontFamilyList",
@@ -454,16 +456,17 @@ servo-owned-types = [
 ]
 servo-immutable-borrow-types = [
     "RawGeckoNode",
     "RawGeckoElement",
     "RawGeckoDocument",
     "RawServoDeclarationBlockStrong",
     "RawGeckoPresContext",
     "RawGeckoStyleAnimationList",
+    "RawGeckoXBLBinding",
 ]
 servo-borrow-types = [
     "nsCSSPropertyIDSet",
     "nsCSSValue",
     "nsTimingFunction",
     "RawGeckoAnimationPropertySegment",
     "RawGeckoAnimationValueList",
     "RawGeckoComputedTiming",