--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -226,21 +226,16 @@ DOMInterfaces = {
     'nativeType': 'nsCSSKeyframesRule',
     'headerFile': 'nsCSSRules.h',
 },
 
 'CSSLexer': {
     'wrapperCache': False
 },
 
-'CSSMozDocumentRule': {
-    'nativeType': 'mozilla::css::DocumentRule',
-    'headerFile': 'nsCSSRules.h',
-},
-
 'CSSPrimitiveValue': {
     'nativeType': 'nsROCSSPrimitiveValue',
 },
 
 'CSSRule': {
     'concrete': False,
     'nativeType': 'mozilla::css::Rule'
 },

new file mode 100644
--- /dev/null
+++ b/layout/style/CSSMozDocumentRule.cpp
@@ -0,0 +1,58 @@
+/* -*- 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/CSSMozDocumentRule.h"
+#include "mozilla/dom/CSSMozDocumentRuleBinding.h"
+
+namespace mozilla {
+namespace dom {
+
+NS_IMPL_ADDREF_INHERITED(CSSMozDocumentRule, css::ConditionRule)
+NS_IMPL_RELEASE_INHERITED(CSSMozDocumentRule, css::ConditionRule)
+
+// QueryInterface implementation for CSSMozDocumentRule
+NS_INTERFACE_MAP_BEGIN(CSSMozDocumentRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSGroupingRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSConditionRule)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSMozDocumentRule)
+NS_INTERFACE_MAP_END_INHERITING(ConditionRule)
+
+// nsIDOMCSSGroupingRule methods
+NS_IMETHODIMP
+CSSMozDocumentRule::GetCssRules(nsIDOMCSSRuleList** aRuleList)
+{
+  return GroupRule::GetCssRules(aRuleList);
+}
+
+NS_IMETHODIMP
+CSSMozDocumentRule::InsertRule(const nsAString & aRule,
+                               uint32_t aIndex, uint32_t* _retval)
+{
+  return GroupRule::InsertRule(aRule, aIndex, _retval);
+}
+
+NS_IMETHODIMP
+CSSMozDocumentRule::DeleteRule(uint32_t aIndex)
+{
+  return GroupRule::DeleteRule(aIndex);
+}
+
+void
+CSSMozDocumentRule::SetConditionText(const nsAString& aConditionText,
+                                     ErrorResult& aRv)
+{
+  aRv = SetConditionText(aConditionText);
+}
+
+/* virtual */ JSObject*
+CSSMozDocumentRule::WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto)
+{
+  return CSSMozDocumentRuleBinding::Wrap(aCx, this, aGivenProto);
+}
+
+} // namespace dom
+} // namespace mozilla

new file mode 100644
--- /dev/null
+++ b/layout/style/CSSMozDocumentRule.h
@@ -0,0 +1,53 @@
+/* -*- 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_CSSMozDocumentRule_h
+#define mozilla_dom_CSSMozDocumentRule_h
+
+#include "mozilla/css/GroupRule.h"
+#include "nsIDOMCSSMozDocumentRule.h"
+
+namespace mozilla {
+namespace dom {
+
+class CSSMozDocumentRule : public css::ConditionRule
+                         , public nsIDOMCSSMozDocumentRule
+{
+protected:
+  using ConditionRule::ConditionRule;
+  virtual ~CSSMozDocumentRule() {}
+
+public:
+  NS_DECL_ISUPPORTS_INHERITED
+
+  int32_t GetType() const final override { return css::Rule::DOCUMENT_RULE; }
+  using Rule::GetType;
+
+  // nsIDOMCSSGroupingRule interface
+  NS_DECL_NSIDOMCSSGROUPINGRULE
+
+  // nsIDOMCSSConditionRule interface
+  NS_IMETHOD SetConditionText(const nsAString& aConditionText) override = 0;
+
+  // nsIDOMCSSMozDocumentRule interface
+  NS_DECL_NSIDOMCSSMOZDOCUMENTRULE
+
+  // WebIDL interface
+  uint16_t Type() const final override {
+    return nsIDOMCSSRule::DOCUMENT_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_CSSMozDocumentRule_h

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -129,16 +129,17 @@ EXPORTS.mozilla += [
     'StyleSheetInlines.h',
     'URLExtraData.h',
 ]
 
 EXPORTS.mozilla.dom += [
     'CSS.h',
     'CSSLexer.h',
     'CSSMediaRule.h',
+    'CSSMozDocumentRule.h',
     'CSSNamespaceRule.h',
     'CSSPageRule.h',
     'CSSRuleList.h',
     'CSSSupportsRule.h',
     'CSSValue.h',
     'FontFace.h',
     'FontFaceSet.h',
     'FontFaceSetIterator.h',
@@ -162,16 +163,17 @@ EXPORTS.mozilla.css += [
 
 UNIFIED_SOURCES += [
     'AnimationCollection.cpp',
     'BindingStyleRule.cpp',
     'CounterStyleManager.cpp',
     'CSS.cpp',
     'CSSLexer.cpp',
     'CSSMediaRule.cpp',
+    'CSSMozDocumentRule.cpp',
     'CSSPageRule.cpp',
     'CSSRuleList.cpp',
     'CSSStyleSheet.cpp',
     'CSSSupportsRule.cpp',
     'CSSVariableDeclarations.cpp',
     'CSSVariableResolver.cpp',
     'CSSVariableValues.cpp',
     'Declaration.cpp',

--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -31,17 +31,16 @@
 #include "nsContentUtils.h"
 #include "nsError.h"
 #include "nsStyleUtil.h"
 #include "mozilla/DeclarationBlockInlines.h"
 #include "nsCSSParser.h"
 #include "nsDOMClassInfoID.h"
 #include "mozilla/dom/CSSStyleDeclarationBinding.h"
 #include "mozilla/dom/CSSImportRuleBinding.h"
-#include "mozilla/dom/CSSMozDocumentRuleBinding.h"
 #include "mozilla/dom/CSSFontFaceRuleBinding.h"
 #include "mozilla/dom/CSSFontFeatureValuesRuleBinding.h"
 #include "mozilla/dom/CSSKeyframeRuleBinding.h"
 #include "mozilla/dom/CSSKeyframesRuleBinding.h"
 #include "mozilla/dom/CSSCounterStyleRuleBinding.h"
 #include "StyleRule.h"
 #include "nsFont.h"
 #include "nsIURI.h"
@@ -521,39 +520,36 @@ MediaRule::AppendConditionText(nsAString
   if (mMedia) {
     nsAutoString mediaText;
     mMedia->GetText(mediaText);
     aOutput.Append(mediaText);
   }
 }
 
 DocumentRule::DocumentRule(uint32_t aLineNumber, uint32_t aColumnNumber)
-  : ConditionRule(aLineNumber, aColumnNumber)
+  : dom::CSSMozDocumentRule(aLineNumber, aColumnNumber)
 {
 }
 
 DocumentRule::DocumentRule(const DocumentRule& aCopy)
-  : ConditionRule(aCopy)
+  : dom::CSSMozDocumentRule(aCopy)
   , mURLs(new URL(*aCopy.mURLs))
 {
 }
 
 DocumentRule::~DocumentRule()
 {
 }
 
 NS_IMPL_ADDREF_INHERITED(DocumentRule, ConditionRule)
 NS_IMPL_RELEASE_INHERITED(DocumentRule, ConditionRule)
 
 // QueryInterface implementation for DocumentRule
 NS_INTERFACE_MAP_BEGIN(DocumentRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSGroupingRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSConditionRule)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMCSSMozDocumentRule)
-NS_INTERFACE_MAP_END_INHERITING(ConditionRule)
+NS_INTERFACE_MAP_END_INHERITING(dom::CSSMozDocumentRule)
 
 #ifdef DEBUG
 /* virtual */ void
 DocumentRule::List(FILE* out, int32_t aIndent) const
 {
   nsAutoCString indentStr;
   for (int32_t indent = aIndent; --indent >= 0; ) {
     indentStr.AppendLiteral("  ");
@@ -585,85 +581,46 @@ DocumentRule::List(FILE* out, int32_t aI
   fprintf_stderr(out, "%s%s {\n", indentStr.get(), str.get());
 
   GroupRule::List(out, aIndent);
 
   fprintf_stderr(out, "%s}\n", indentStr.get());
 }
 #endif
 
-/* virtual */ int32_t
-DocumentRule::GetType() const
-{
-  return Rule::DOCUMENT_RULE;
-}
-
 /* virtual */ already_AddRefed<Rule>
 DocumentRule::Clone() const
 {
   RefPtr<Rule> clone = new DocumentRule(*this);
   return clone.forget();
 }
 
-uint16_t
-DocumentRule::Type() const
-{
-  // XXX What should really happen here?
-  return nsIDOMCSSRule::UNKNOWN_RULE;
-}
-
 void
 DocumentRule::GetCssTextImpl(nsAString& aCssText) const
 {
   aCssText.AssignLiteral("@-moz-document ");
   AppendConditionText(aCssText);
   GroupRule::AppendRulesToCssText(aCssText);
 }
 
-// nsIDOMCSSGroupingRule methods
-NS_IMETHODIMP
-DocumentRule::GetCssRules(nsIDOMCSSRuleList* *aRuleList)
-{
-  return GroupRule::GetCssRules(aRuleList);
-}
-
-NS_IMETHODIMP
-DocumentRule::InsertRule(const nsAString & aRule, uint32_t aIndex, uint32_t* _retval)
-{
-  return GroupRule::InsertRule(aRule, aIndex, _retval);
-}
-
-NS_IMETHODIMP
-DocumentRule::DeleteRule(uint32_t aIndex)
-{
-  return GroupRule::DeleteRule(aIndex);
-}
-
 // nsIDOMCSSConditionRule methods
 NS_IMETHODIMP
 DocumentRule::GetConditionText(nsAString& aConditionText)
 {
   aConditionText.Truncate(0);
   AppendConditionText(aConditionText);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 DocumentRule::SetConditionText(const nsAString& aConditionText)
 {
   return NS_ERROR_NOT_IMPLEMENTED;
 }
 
-void
-DocumentRule::SetConditionText(const nsAString& aConditionText,
-                               ErrorResult& aRv)
-{
-  aRv.Throw(NS_ERROR_NOT_IMPLEMENTED);
-}
-
 // GroupRule interface
 /* virtual */ bool
 DocumentRule::UseForPresentation(nsPresContext* aPresContext,
                                  nsMediaQueryResultCacheKey& aKey)
 {
   return UseForPresentation(aPresContext);
 }
 
@@ -748,23 +705,16 @@ DocumentRule::SizeOfIncludingThis(Malloc
 
   // Measurement of the following members may be added later if DMD finds it is
   // worthwhile:
   // - mURLs
 
   return n;
 }
 
-/* virtual */ JSObject*
-DocumentRule::WrapObject(JSContext* aCx,
-                         JS::Handle<JSObject*> aGivenProto)
-{
-  return CSSMozDocumentRuleBinding::Wrap(aCx, this, aGivenProto);
-}
-
 void
 DocumentRule::AppendConditionText(nsAString& aCssText) const
 {
   for (URL *url = mURLs; url; url = url->next) {
     switch (url->func) {
       case URLMatchingFunction::eURL:
         aCssText.AppendLiteral("url(");
         break;

--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -16,16 +16,17 @@
 #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/CSSMediaRule.h"
 #include "mozilla/dom/CSSPageRule.h"
 #include "mozilla/dom/CSSSupportsRule.h"
+#include "mozilla/dom/CSSMozDocumentRule.h"
 #include "nsAutoPtr.h"
 #include "nsCSSPropertyID.h"
 #include "nsCSSValue.h"
 #include "nsDOMCSSDeclaration.h"
 #include "nsIDOMCSSConditionRule.h"
 #include "nsIDOMCSSCounterStyleRule.h"
 #include "nsIDOMCSSFontFeatureValuesRule.h"
 #include "nsIDOMCSSGroupingRule.h"
@@ -89,45 +90,36 @@ public:
     const override MOZ_MUST_OVERRIDE;
 
 protected:
   void AppendConditionText(nsAString& aOutput) const;
 
   RefPtr<nsMediaList> mMedia;
 };
 
-class DocumentRule final : public ConditionRule,
-                           public nsIDOMCSSMozDocumentRule
+class DocumentRule final : public dom::CSSMozDocumentRule
 {
 public:
   DocumentRule(uint32_t aLineNumber, uint32_t aColumnNumber);
 private:
   DocumentRule(const DocumentRule& aCopy);
   ~DocumentRule();
 public:
 
   NS_DECL_ISUPPORTS_INHERITED
 
   // Rule methods
 #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<Rule> Clone() const override;
 
-  // nsIDOMCSSGroupingRule interface
-  NS_DECL_NSIDOMCSSGROUPINGRULE
-
   // nsIDOMCSSConditionRule interface
   NS_DECL_NSIDOMCSSCONDITIONRULE
 
-  // nsIDOMCSSMozDocumentRule interface
-  NS_DECL_NSIDOMCSSMOZDOCUMENTRULE
-
   // rest of GroupRule
   virtual bool UseForPresentation(nsPresContext* aPresContext,
                                   nsMediaQueryResultCacheKey& aKey) override;
 
   bool UseForPresentation(nsPresContext* aPresContext);
 
   static bool UseForPresentation(nsIDocument* aDoc,
                                  nsIURI* aDocURI,
@@ -148,28 +140,22 @@ public:
     {
     }
     ~URL();
   };
 
   void SetURLs(URL *aURLs) { mURLs = aURLs; }
 
   // 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::CSSMozDocumentRule::SetConditionText;
 
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)
     const override MOZ_MUST_OVERRIDE;
 
-  virtual JSObject* WrapObject(JSContext* aCx,
-                               JS::Handle<JSObject*> aGivenProto) override;
-
 protected:
   void AppendConditionText(nsAString& aOutput) const;
 
   nsAutoPtr<URL> mURLs; // linked list of |struct URL| above.
 };
 
 } // namespace css