--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -198,21 +198,16 @@ DOMInterfaces = {
     'headerFile': 'nsCSSCounterStyleRule.h',
 },
 
 'CSSFontFaceRule': {
     'nativeType': 'nsCSSFontFaceRule',
     'headerFile': 'nsCSSFontFaceRule.h',
 },
 
-'CSSFontFeatureValuesRule': {
-    'nativeType': 'nsCSSFontFeatureValuesRule',
-    'headerFile': 'nsCSSRules.h',
-},
-
 'CSSGroupingRule': {
     'concrete': False,
     'nativeType': 'mozilla::css::GroupRule',
 },
 
 'CSSLexer': {
     'wrapperCache': False
 },

new file mode 100644
--- /dev/null
+++ b/layout/style/CSSFontFeatureValuesRule.cpp
@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "mozilla/dom/CSSFontFeatureValuesRule.h"
+#include "mozilla/dom/CSSFontFeatureValuesRuleBinding.h"
+
+namespace mozilla {
+namespace dom {
+
+NS_IMPL_ADDREF_INHERITED(CSSFontFeatureValuesRule, css::Rule)
+NS_IMPL_RELEASE_INHERITED(CSSFontFeatureValuesRule, css::Rule)
+
+// QueryInterface implementation for CSSFontFeatureValuesRule
+// If this ever gets its own cycle-collection bits, reevaluate our IsCCLeaf
+// implementation.
+NS_INTERFACE_MAP_BEGIN(CSSFontFeatureValuesRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSFontFeatureValuesRule)
+NS_INTERFACE_MAP_END_INHERITING(mozilla::css::Rule)
+
+void
+CSSFontFeatureValuesRule::SetFontFamily(const nsAString& aFamily,
+                                              ErrorResult& aRv)
+{
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+}
+
+void
+CSSFontFeatureValuesRule::SetValueText(const nsAString& aFamily,
+                                             ErrorResult& aRv)
+{
+  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
+}
+
+bool
+CSSFontFeatureValuesRule::IsCCLeaf() const
+{
+  return Rule::IsCCLeaf();
+}
+
+/* virtual */ JSObject*
+CSSFontFeatureValuesRule::WrapObject(JSContext* aCx,
+                                       JS::Handle<JSObject*> aGivenProto)
+{
+  return CSSFontFeatureValuesRuleBinding::Wrap(aCx, this, aGivenProto);
+}
+
+} // namespace dom
+} // namespace mozilla

new file mode 100644
--- /dev/null
+++ b/layout/style/CSSFontFeatureValuesRule.h
@@ -0,0 +1,56 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 mozilla_dom_CSSFontFeatureValuesRule_h
+#define mozilla_dom_CSSFontFeatureValuesRule_h
+
+#include "mozilla/css/Rule.h"
+
+#include "nsICSSDeclaration.h"
+#include "nsIDOMCSSFontFeatureValuesRule.h"
+#include "nsIDOMCSSStyleDeclaration.h"
+
+namespace mozilla {
+namespace dom {
+
+class CSSFontFeatureValuesRule : public css::Rule
+                               , public nsIDOMCSSFontFeatureValuesRule
+{
+public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  virtual bool IsCCLeaf() const override;
+
+  int32_t GetType() const final { return Rule::FONT_FEATURE_VALUES_RULE; }
+  using Rule::GetType;
+  virtual already_AddRefed<mozilla::css::Rule> Clone() const override = 0;
+
+  using nsIDOMCSSFontFeatureValuesRule::SetFontFamily;
+  using nsIDOMCSSFontFeatureValuesRule::SetValueText;
+  // WebIDL interfaces
+  uint16_t Type() const final { return nsIDOMCSSRule::FONT_FEATURE_VALUES_RULE; }
+  virtual void GetCssTextImpl(nsAString& aCssText) const override = 0;
+  // The XPCOM GetFontFamily is fine
+  void SetFontFamily(const nsAString& aFamily, mozilla::ErrorResult& aRv);
+  // The XPCOM GetValueText is fine
+  void SetValueText(const nsAString& aFamily, mozilla::ErrorResult& aRv);
+
+  virtual size_t
+  SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override = 0;
+
+  JSObject*
+  WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
+
+protected:
+  using Rule::Rule;
+
+  virtual ~CSSFontFeatureValuesRule() {};
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_CSSFontFeatureValuesRule_h

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -135,16 +135,17 @@ EXPORTS.mozilla += [
     'StyleSheet.h',
     'StyleSheetInfo.h',
     'StyleSheetInlines.h',
     'URLExtraData.h',
 ]
 
 EXPORTS.mozilla.dom += [
     'CSS.h',
+    'CSSFontFeatureValuesRule.h',
     'CSSImportRule.h',
     'CSSKeyframeRule.h',
     'CSSKeyframesRule.h',
     'CSSLexer.h',
     'CSSMediaRule.h',
     'CSSMozDocumentRule.h',
     'CSSNamespaceRule.h',
     'CSSPageRule.h',
@@ -172,16 +173,17 @@ EXPORTS.mozilla.css += [
     'URLMatchingFunction.h',
 ]
 
 UNIFIED_SOURCES += [
     'AnimationCollection.cpp',
     'BindingStyleRule.cpp',
     'CounterStyleManager.cpp',
     'CSS.cpp',
+    'CSSFontFeatureValuesRule.cpp',
     'CSSImportRule.cpp',
     'CSSKeyframeRule.cpp',
     'CSSKeyframesRule.cpp',
     'CSSLexer.cpp',
     'CSSMediaRule.cpp',
     'CSSMozDocumentRule.cpp',
     'CSSPageRule.cpp',
     'CSSRuleList.cpp',

--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -1260,31 +1260,24 @@ nsCSSFontFaceRule::WrapObject(JSContext*
 
 /* virtual */ already_AddRefed<css::Rule>
 nsCSSFontFeatureValuesRule::Clone() const
 {
   RefPtr<css::Rule> clone = new nsCSSFontFeatureValuesRule(*this);
   return clone.forget();
 }
 
-NS_IMPL_ADDREF_INHERITED(nsCSSFontFeatureValuesRule, mozilla::css::Rule)
-NS_IMPL_RELEASE_INHERITED(nsCSSFontFeatureValuesRule, mozilla::css::Rule)
+NS_IMPL_ADDREF_INHERITED(nsCSSFontFeatureValuesRule, dom::CSSFontFeatureValuesRule)
+NS_IMPL_RELEASE_INHERITED(nsCSSFontFeatureValuesRule, dom::CSSFontFeatureValuesRule)
 
 // QueryInterface implementation for nsCSSFontFeatureValuesRule
 // If this ever gets its own cycle-collection bits, reevaluate our IsCCLeaf
 // implementation.
 NS_INTERFACE_MAP_BEGIN(nsCSSFontFeatureValuesRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSFontFeatureValuesRule)
-NS_INTERFACE_MAP_END_INHERITING(mozilla::css::Rule)
-
-bool
-nsCSSFontFeatureValuesRule::IsCCLeaf() const
-{
-  return Rule::IsCCLeaf();
-}
+NS_INTERFACE_MAP_END_INHERITING(dom::CSSFontFeatureValuesRule)
 
 static void
 FeatureValuesToString(
   const nsTArray<gfxFontFeatureValueSet::FeatureValues>& aFeatureValues,
   nsAString& aOutStr)
 {
   uint32_t i, n;
 
@@ -1358,74 +1351,48 @@ nsCSSFontFeatureValuesRule::List(FILE* o
   nsAutoCString indentStr;
   for (i = aIndent; --i >= 0; ) {
     indentStr.AppendLiteral("  ");
   }
   fprintf_stderr(out, "%s%s\n", indentStr.get(), utf8.get());
 }
 #endif
 
-/* virtual */ int32_t
-nsCSSFontFeatureValuesRule::GetType() const
-{
-  return Rule::FONT_FEATURE_VALUES_RULE;
-}
-
-uint16_t
-nsCSSFontFeatureValuesRule::Type() const
-{
-  return nsIDOMCSSRule::FONT_FEATURE_VALUES_RULE;
-}
-
-void
-nsCSSFontFeatureValuesRule::GetCssTextImpl(nsAString& aCssText) const
-{
-  FontFeatureValuesRuleToString(mFamilyList, mFeatureValues, aCssText);
-}
-
-void
-nsCSSFontFeatureValuesRule::SetFontFamily(const nsAString& aFamily,
-                                          ErrorResult& aRv)
-{
-  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
-}
-
-void
-nsCSSFontFeatureValuesRule::SetValueText(const nsAString& aFamily,
-                                         ErrorResult& aRv)
-{
-  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
-}
-
 NS_IMETHODIMP
 nsCSSFontFeatureValuesRule::GetFontFamily(nsAString& aFamilyListStr)
 {
   nsStyleUtil::AppendEscapedCSSFontFamilyList(mFamilyList, aFamilyListStr);
   return NS_OK;
 }
 
 NS_IMETHODIMP
+nsCSSFontFeatureValuesRule::GetValueText(nsAString& aValueText)
+{
+  FeatureValuesToString(mFeatureValues, aValueText);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
 nsCSSFontFeatureValuesRule::SetFontFamily(const nsAString& aFontFamily)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP
-nsCSSFontFeatureValuesRule::GetValueText(nsAString& aValueText)
-{
-  FeatureValuesToString(mFeatureValues, aValueText);
-  return NS_OK;
-}
-
-NS_IMETHODIMP
 nsCSSFontFeatureValuesRule::SetValueText(const nsAString& aValueText)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
+void
+nsCSSFontFeatureValuesRule::GetCssTextImpl(nsAString& aCssText) const
+{
+  FontFeatureValuesRuleToString(mFamilyList, mFeatureValues, aCssText);
+}
+
 struct MakeFamilyArray {
   explicit MakeFamilyArray(nsTArray<nsString>& aFamilyArray)
     : familyArray(aFamilyArray), hasGeneric(false)
   {}
 
   static bool
   AddFamily(const nsString& aFamily, bool aGeneric, void* aData)
   {
@@ -1478,23 +1445,16 @@ nsCSSFontFeatureValuesRule::AddValueList
 
 size_t
 nsCSSFontFeatureValuesRule::SizeOfIncludingThis(
   MallocSizeOf aMallocSizeOf) const
 {
   return aMallocSizeOf(this);
 }
 
-/* virtual */ JSObject*
-nsCSSFontFeatureValuesRule::WrapObject(JSContext* aCx,
-                                       JS::Handle<JSObject*> aGivenProto)
-{
-  return CSSFontFeatureValuesRuleBinding::Wrap(aCx, this, aGivenProto);
-}
-
 // -------------------------------------------
 // nsCSSKeyframeStyleDeclaration
 //
 
 nsCSSKeyframeStyleDeclaration::nsCSSKeyframeStyleDeclaration(nsCSSKeyframeRule *aRule)
   : mRule(aRule)
 {
 }

--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -13,16 +13,17 @@
 #include "StyleRule.h"
 #include "gfxFontFeatures.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Move.h"
 #include "mozilla/SheetType.h"
 #include "mozilla/css/GroupRule.h"
 #include "mozilla/css/URLMatchingFunction.h"
+#include "mozilla/dom/CSSFontFeatureValuesRule.h"
 #include "mozilla/dom/CSSKeyframeRule.h"
 #include "mozilla/dom/CSSKeyframesRule.h"
 #include "mozilla/dom/CSSMediaRule.h"
 #include "mozilla/dom/CSSPageRule.h"
 #include "mozilla/dom/CSSSupportsRule.h"
 #include "mozilla/dom/CSSMozDocumentRule.h"
 #include "nsAutoPtr.h"
 #include "nsCSSPropertyID.h"
@@ -155,70 +156,58 @@ protected:
 
   nsAutoPtr<URL> mURLs; // linked list of |struct URL| above.
 };
 
 } // namespace css
 
 } // namespace mozilla
 
-class nsCSSFontFeatureValuesRule final : public mozilla::css::Rule,
-                                         public nsIDOMCSSFontFeatureValuesRule
+class nsCSSFontFeatureValuesRule final : public mozilla::dom::CSSFontFeatureValuesRule
 {
 public:
   nsCSSFontFeatureValuesRule(uint32_t aLineNumber, uint32_t aColumnNumber)
-    : mozilla::css::Rule(aLineNumber, aColumnNumber)
+    : mozilla::dom::CSSFontFeatureValuesRule(aLineNumber, aColumnNumber)
   {
   }
 
   nsCSSFontFeatureValuesRule(const nsCSSFontFeatureValuesRule& aCopy)
     // copy everything except our reference count
-    : mozilla::css::Rule(aCopy),
+    : mozilla::dom::CSSFontFeatureValuesRule(aCopy),
       mFamilyList(aCopy.mFamilyList),
       mFeatureValues(aCopy.mFeatureValues)
   {
   }
 
   NS_DECL_ISUPPORTS_INHERITED
-  virtual bool IsCCLeaf() const override;
 
 #ifdef DEBUG
   virtual void List(FILE* out = stdout, int32_t aIndent = 0) const override;
 #endif
-  virtual int32_t GetType() const override;
-  using Rule::GetType;
   virtual already_AddRefed<mozilla::css::Rule> Clone() const override;
 
-  // nsIDOMCSSFontFaceRule interface
+  // nsIDOMCSSFontFeatureValuesRule interface
   NS_DECL_NSIDOMCSSFONTFEATUREVALUESRULE
 
   // WebIDL interface
-  uint16_t Type() const override;
-  void GetCssTextImpl(nsAString& aCssText) const override;
-  // The XPCOM GetFontFamily is fine
-  void SetFontFamily(const nsAString& aFamily, mozilla::ErrorResult& aRv);
-  // The XPCOM GetValueText is fine
-  void SetValueText(const nsAString& aFamily, mozilla::ErrorResult& aRv);
+  void GetCssTextImpl(nsAString& aCssText) const final;
 
   const mozilla::FontFamilyList& GetFamilyList() { return mFamilyList; }
   void SetFamilyList(const mozilla::FontFamilyList& aFamilyList);
 
   void AddValueList(int32_t aVariantAlternate,
                     nsTArray<gfxFontFeatureValueSet::ValueList>& aValueList);
 
   const nsTArray<gfxFontFeatureValueSet::FeatureValues>& GetFeatureValues()
   {
     return mFeatureValues;
   }
 
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
 
-  virtual JSObject* WrapObject(JSContext* aCx,
-                               JS::Handle<JSObject*> aGivenProto) override;
-
 protected:
   ~nsCSSFontFeatureValuesRule() {}
 
   mozilla::FontFamilyList mFamilyList;
   nsTArray<gfxFontFeatureValueSet::FeatureValues> mFeatureValues;
 };
 
 class nsCSSKeyframeRule;