diff --git a/dom/bindings/Bindings.conf b/dom/bindings/Bindings.conf
index 899e7bd98b2c..f83aa007f55a 100644
--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -258,11 +258,6 @@ DOMInterfaces = {
     'binaryNames': { 'ownerRule': 'DOMOwnerRule' },
 },
 
-'CSSSupportsRule': {
-    'nativeType': 'mozilla::CSSSupportsRule',
-    'headerFile': 'nsCSSRules.h',
-},
-
 'CSSValue': {
     'concrete': False
 },
diff --git a/layout/style/CSSSupportsRule.cpp b/layout/style/CSSSupportsRule.cpp
new file mode 100644
index 000000000000..0ee88b0ae146
--- /dev/null
+++ b/layout/style/CSSSupportsRule.cpp
@@ -0,0 +1,60 @@
+/* -*- 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/CSSSupportsRule.h"
+
+#include "mozilla/dom/CSSSupportsRuleBinding.h"
+
+using namespace mozilla::css;
+
+namespace mozilla {
+namespace dom {
+
+NS_IMPL_ADDREF_INHERITED(CSSSupportsRule, css::ConditionRule)
+NS_IMPL_RELEASE_INHERITED(CSSSupportsRule, css::ConditionRule)
+
+// QueryInterface implementation for CSSSupportsRule
+NS_INTERFACE_MAP_BEGIN(CSSSupportsRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSGroupingRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSConditionRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSSupportsRule)
+NS_INTERFACE_MAP_END_INHERITING(ConditionRule)
+
+// nsIDOMCSSGroupingRule methods
+NS_IMETHODIMP
+CSSSupportsRule::GetCssRules(nsIDOMCSSRuleList** aRuleList)
+{
+  return GroupRule::GetCssRules(aRuleList);
+}
+
+NS_IMETHODIMP
+CSSSupportsRule::InsertRule(const nsAString & aRule, uint32_t aIndex, uint32_t* _retval)
+{
+  return GroupRule::InsertRule(aRule, aIndex, _retval);
+}
+
+NS_IMETHODIMP
+CSSSupportsRule::DeleteRule(uint32_t aIndex)
+{
+  return GroupRule::DeleteRule(aIndex);
+}
+
+void
+CSSSupportsRule::SetConditionText(const nsAString& aConditionText,
+                                  ErrorResult& aRv)
+{
+  aRv = SetConditionText(aConditionText);
+}
+
+/* virtual */ JSObject*
+CSSSupportsRule::WrapObject(JSContext* aCx,
+                            JS::Handle<JSObject*> aGivenProto)
+{
+  return CSSSupportsRuleBinding::Wrap(aCx, this, aGivenProto);
+}
+
+} // namespace dom
+} // namespace mozilla
diff --git a/layout/style/CSSSupportsRule.h b/layout/style/CSSSupportsRule.h
new file mode 100644
index 000000000000..d42bfe0a05a3
--- /dev/null
+++ b/layout/style/CSSSupportsRule.h
@@ -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/. */
+
+#ifndef mozilla_dom_CSSSupportsRule_h
+#define mozilla_dom_CSSSupportsRule_h
+
+#include "mozilla/css/GroupRule.h"
+#include "nsIDOMCSSSupportsRule.h"
+
+namespace mozilla {
+namespace dom {
+
+class CSSSupportsRule : public css::ConditionRule
+                      , public nsIDOMCSSSupportsRule
+{
+protected:
+  using ConditionRule::ConditionRule;
+  virtual ~CSSSupportsRule() {}
+
+public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  int32_t GetType() const override { return css::Rule::SUPPORTS_RULE; }
+  using Rule::GetType;
+
+  // nsIDOMCSSGroupingRule interface
+  NS_DECL_NSIDOMCSSGROUPINGRULE
+
+  // nsIDOMCSSConditionRule interface
+  NS_IMETHOD SetConditionText(const nsAString& aConditionText) override = 0;
+
+  // nsIDOMCSSSupportsRule interface
+  NS_DECL_NSIDOMCSSSUPPORTSRULE
+
+  // WebIDL interface
+  uint16_t Type() const override { return nsIDOMCSSRule::SUPPORTS_RULE; }
+  // Our XPCOM GetConditionText is OK
+  void SetConditionText(const nsAString& aConditionText,
+                        ErrorResult& aRv) final;
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_CSSSupportsRule_h
diff --git a/layout/style/moz.build b/layout/style/moz.build
index 2bbe04134d93..0c8d67626542 100644
--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -134,6 +134,7 @@ EXPORTS.mozilla.dom += [
     'CSSNamespaceRule.h',
     'CSSPageRule.h',
     'CSSRuleList.h',
+    'CSSSupportsRule.h',
     'CSSValue.h',
     'FontFace.h',
     'FontFaceSet.h',
@@ -165,6 +166,7 @@ UNIFIED_SOURCES += [
     'CSSPageRule.cpp',
     'CSSRuleList.cpp',
     'CSSStyleSheet.cpp',
+    'CSSSupportsRule.cpp',
     'CSSVariableDeclarations.cpp',
     'CSSVariableResolver.cpp',
     'CSSVariableValues.cpp',
diff --git a/layout/style/nsCSSRules.cpp b/layout/style/nsCSSRules.cpp
index 99ce9928c8f9..f012ff995f18 100644
--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -36,7 +36,6 @@
 #include "nsDOMClassInfoID.h"
 #include "mozilla/dom/CSSStyleDeclarationBinding.h"
 #include "mozilla/dom/CSSImportRuleBinding.h"
-#include "mozilla/dom/CSSSupportsRuleBinding.h"
 #include "mozilla/dom/CSSMozDocumentRuleBinding.h"
 #include "mozilla/dom/CSSFontFaceRuleBinding.h"
 #include "mozilla/dom/CSSFontFeatureValuesRuleBinding.h"
@@ -2272,7 +2271,7 @@ namespace mozilla {
 CSSSupportsRule::CSSSupportsRule(bool aConditionMet,
                                  const nsString& aCondition,
                                  uint32_t aLineNumber, uint32_t aColumnNumber)
-  : css::ConditionRule(aLineNumber, aColumnNumber)
+  : dom::CSSSupportsRule(aLineNumber, aColumnNumber)
   , mUseGroup(aConditionMet)
   , mCondition(aCondition)
 {
@@ -2283,7 +2282,7 @@ CSSSupportsRule::~CSSSupportsRule()
 }
 
 CSSSupportsRule::CSSSupportsRule(const CSSSupportsRule& aCopy)
-  : css::ConditionRule(aCopy),
+  : dom::CSSSupportsRule(aCopy),
     mUseGroup(aCopy.mUseGroup),
     mCondition(aCopy.mCondition)
 {
@@ -2307,12 +2306,6 @@ CSSSupportsRule::List(FILE* out, int32_t aIndent) const
 }
 #endif
 
-/* virtual */ int32_t
-CSSSupportsRule::GetType() const
-{
-  return Rule::SUPPORTS_RULE;
-}
-
 /* virtual */ already_AddRefed<mozilla::css::Rule>
 CSSSupportsRule::Clone() const
 {
@@ -2332,16 +2325,7 @@ NS_IMPL_RELEASE_INHERITED(CSSSupportsRule, css::ConditionRule)
 
 // QueryInterface implementation for CSSSupportsRule
 NS_INTERFACE_MAP_BEGIN(CSSSupportsRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSGroupingRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSConditionRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSSupportsRule)
-NS_INTERFACE_MAP_END_INHERITING(ConditionRule)
-
-uint16_t
-CSSSupportsRule::Type() const
-{
-  return nsIDOMCSSRule::SUPPORTS_RULE;
-}
+NS_INTERFACE_MAP_END_INHERITING(dom::CSSSupportsRule)
 
 void
 CSSSupportsRule::GetCssTextImpl(nsAString& aCssText) const
@@ -2351,25 +2335,6 @@ CSSSupportsRule::GetCssTextImpl(nsAString& aCssText) const
   css::GroupRule::AppendRulesToCssText(aCssText);
 }
 
-// nsIDOMCSSGroupingRule methods
-NS_IMETHODIMP
-CSSSupportsRule::GetCssRules(nsIDOMCSSRuleList* *aRuleList)
-{
-  return css::GroupRule::GetCssRules(aRuleList);
-}
-
-NS_IMETHODIMP
-CSSSupportsRule::InsertRule(const nsAString & aRule, uint32_t aIndex, uint32_t* _retval)
-{
-  return css::GroupRule::InsertRule(aRule, aIndex, _retval);
-}
-
-NS_IMETHODIMP
-CSSSupportsRule::DeleteRule(uint32_t aIndex)
-{
-  return css::GroupRule::DeleteRule(aIndex);
-}
-
 // nsIDOMCSSConditionRule methods
 NS_IMETHODIMP
 CSSSupportsRule::GetConditionText(nsAString& aConditionText)
@@ -2384,13 +2349,6 @@ CSSSupportsRule::SetConditionText(const nsAString& aConditionText)
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
-void
-CSSSupportsRule::SetConditionText(const nsAString& aConditionText,
-                                  ErrorResult& aRv)
-{
-  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
-}
-
 /* virtual */ size_t
 CSSSupportsRule::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
 {
@@ -2400,13 +2358,6 @@ CSSSupportsRule::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
   return n;
 }
 
-/* virtual */ JSObject*
-CSSSupportsRule::WrapObject(JSContext* aCx,
-                            JS::Handle<JSObject*> aGivenProto)
-{
-  return CSSSupportsRuleBinding::Wrap(aCx, this, aGivenProto);
-}
-
 } // namespace mozilla
 
 // -------------------------------------------
diff --git a/layout/style/nsCSSRules.h b/layout/style/nsCSSRules.h
index 0517458f95aa..0f34957c7cba 100644
--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -19,6 +19,7 @@
 #include "mozilla/css/GroupRule.h"
 #include "mozilla/dom/CSSMediaRule.h"
 #include "mozilla/dom/CSSPageRule.h"
+#include "mozilla/dom/CSSSupportsRule.h"
 #include "nsAutoPtr.h"
 #include "nsCSSPropertyID.h"
 #include "nsCSSValue.h"
@@ -446,8 +447,7 @@ private:
 
 namespace mozilla {
 
-class CSSSupportsRule final : public css::ConditionRule,
-                              public nsIDOMCSSSupportsRule
+class CSSSupportsRule final : public dom::CSSSupportsRule
 {
 public:
   CSSSupportsRule(bool aConditionMet, const nsString& aCondition,
@@ -458,35 +458,21 @@ public:
 #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;
   virtual bool UseForPresentation(nsPresContext* aPresContext,
                                   nsMediaQueryResultCacheKey& aKey) override;
 
   NS_DECL_ISUPPORTS_INHERITED
 
-  // nsIDOMCSSGroupingRule interface
-  NS_DECL_NSIDOMCSSGROUPINGRULE
-
   // nsIDOMCSSConditionRule interface
   NS_DECL_NSIDOMCSSCONDITIONRULE
 
-  // nsIDOMCSSSupportsRule interface
-  NS_DECL_NSIDOMCSSSUPPORTSRULE
-
   // WebIDL interface
-  uint16_t Type() const override;
   void GetCssTextImpl(nsAString& aCssText) const override;
-  // Our XPCOM GetConditionText is OK
-  virtual void SetConditionText(const nsAString& aConditionText,
-                                ErrorResult& aRv) override;
+  using dom::CSSSupportsRule::SetConditionText;
 
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
 
-  virtual JSObject* WrapObject(JSContext* aCx,
-                               JS::Handle<JSObject*> aGivenProto) override;
-
 protected:
   virtual ~CSSSupportsRule();