--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -190,17 +190,17 @@ DOMInterfaces = {
 'CSSConditionRule': {
     'concrete': False,
     'nativeType': 'mozilla::css::ConditionRule',
     'headerFile': 'mozilla/css/GroupRule.h',
 },
 
 'CSSCounterStyleRule': {
     'nativeType': 'nsCSSCounterStyleRule',
-    'headerFile': 'nsCSSRules.h',
+    'headerFile': 'nsCSSCounterStyleRule.h',
 },
 
 'CSSFontFaceRule': {
     'nativeType': 'nsCSSFontFaceRule',
     'headerFile': 'nsCSSFontFaceRule.h',
 },
 
 'CSSFontFeatureValuesRule': {

--- a/layout/style/CounterStyleManager.cpp
+++ b/layout/style/CounterStyleManager.cpp
@@ -7,17 +7,17 @@
 #include "CounterStyleManager.h"
 
 #include "mozilla/ArenaObjectID.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/MathAlgorithms.h"
 #include "mozilla/Types.h"
 #include "mozilla/WritingModes.h"
-#include "nsCSSRules.h"
+#include "nsCSSCounterStyleRule.h"
 #include "nsString.h"
 #include "nsStyleSet.h"
 #include "nsTArray.h"
 #include "nsTHashtable.h"
 #include "nsUnicodeProperties.h"
 #include "mozilla/StyleSetHandle.h"
 #include "mozilla/StyleSetHandleInlines.h"
 

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -26,16 +26,17 @@ EXPORTS += [
     '!nsStyleStructList.h',
     'AnimationCommon.h',
     'CounterStyleManager.h',
     'nsAnimationManager.h',
     'nsComputedDOMStylePropertyList.h',
     'nsCSSAnonBoxes.h',
     'nsCSSAnonBoxList.h',
     'nsCSSCounterDescList.h',
+    'nsCSSCounterStyleRule.h',
     'nsCSSFontDescList.h',
     'nsCSSFontFaceRule.h',
     'nsCSSKeywordList.h',
     'nsCSSKeywords.h',
     'nsCSSParser.h',
     'nsCSSPropAliasList.h',
     'nsCSSPropertyID.h',
     'nsCSSPropertyIDSet.h',

new file mode 100644
--- /dev/null
+++ b/layout/style/nsCSSCounterStyleRule.h
@@ -0,0 +1,110 @@
+/* -*- 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 nsCSSCounterStyleRule_h
+#define nsCSSCounterStyleRule_h
+
+#include "mozilla/css/Rule.h"
+#include "nsCSSValue.h"
+#include "nsIDOMCSSCounterStyleRule.h"
+
+class nsCSSCounterStyleRule final : public mozilla::css::Rule,
+                                    public nsIDOMCSSCounterStyleRule
+{
+public:
+  explicit nsCSSCounterStyleRule(nsIAtom* aName,
+                                 uint32_t aLineNumber, uint32_t aColumnNumber)
+    : mozilla::css::Rule(aLineNumber, aColumnNumber)
+    , mName(aName)
+    , mGeneration(0)
+  {
+    MOZ_ASSERT(aName, "Must have non-null name");
+  }
+
+private:
+  nsCSSCounterStyleRule(const nsCSSCounterStyleRule& aCopy);
+  ~nsCSSCounterStyleRule();
+
+public:
+  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;
+
+  // nsIDOMCSSCounterStyleRule
+  NS_DECL_NSIDOMCSSCOUNTERSTYLERULE
+
+  // WebIDL interface
+  uint16_t Type() const override;
+  void GetCssTextImpl(nsAString& aCssText) const override;
+  // The XPCOM GetName is OK
+  // The XPCOM SetName is OK
+  // The XPCOM GetSystem is OK
+  // The XPCOM SetSystem is OK
+  // The XPCOM GetSymbols is OK
+  // The XPCOM SetSymbols is OK
+  // The XPCOM GetAdditiveSymbols is OK
+  // The XPCOM SetAdditiveSymbols is OK
+  // The XPCOM GetNegative is OK
+  // The XPCOM SetNegative is OK
+  // The XPCOM GetPrefix is OK
+  // The XPCOM SetPrefix is OK
+  // The XPCOM GetSuffix is OK
+  // The XPCOM SetSuffix is OK
+  // The XPCOM GetRange is OK
+  // The XPCOM SetRange is OK
+  // The XPCOM GetPad is OK
+  // The XPCOM SetPad is OK
+  // The XPCOM GetSpeakAs is OK
+  // The XPCOM SetSpeakAs is OK
+  // The XPCOM GetFallback is OK
+  // The XPCOM SetFallback is OK
+
+  // This function is only used to check whether a non-empty value, which has
+  // been accepted by parser, is valid for the given system and descriptor.
+  static bool CheckDescValue(int32_t aSystem,
+                             nsCSSCounterDesc aDescID,
+                             const nsCSSValue& aValue);
+
+  nsIAtom* Name() const { return mName; }
+
+  uint32_t GetGeneration() const { return mGeneration; }
+
+  int32_t GetSystem() const;
+  const nsCSSValue& GetSystemArgument() const;
+
+  const nsCSSValue& GetDesc(nsCSSCounterDesc aDescID) const
+  {
+    MOZ_ASSERT(aDescID >= 0 && aDescID < eCSSCounterDesc_COUNT,
+               "descriptor ID out of range");
+    return mValues[aDescID];
+  }
+
+  void SetDesc(nsCSSCounterDesc aDescID, const nsCSSValue& aValue);
+
+  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
+
+  virtual JSObject* WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) override;
+
+private:
+  typedef decltype(&nsCSSCounterStyleRule::GetSymbols) Getter;
+  static const Getter kGetters[];
+
+  nsresult GetDescriptor(nsCSSCounterDesc aDescID, nsAString& aValue);
+  nsresult SetDescriptor(nsCSSCounterDesc aDescID, const nsAString& aValue);
+
+  nsCOMPtr<nsIAtom> mName;
+  nsCSSValue mValues[eCSSCounterDesc_COUNT];
+  uint32_t   mGeneration;
+};
+
+#endif // nsCSSCounterStyleRule_h

--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -25,16 +25,17 @@
 #include "nsCSSKeywords.h"
 #include "nsCSSScanner.h"
 #include "mozilla/css/ErrorReporter.h"
 #include "mozilla/css/Loader.h"
 #include "mozilla/css/StyleRule.h"
 #include "mozilla/css/ImportRule.h"
 #include "mozilla/css/URLMatchingFunction.h"
 #include "nsCSSRules.h"
+#include "nsCSSCounterStyleRule.h"
 #include "nsCSSFontFaceRule.h"
 #include "mozilla/css/NameSpaceRule.h"
 #include "nsTArray.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/css/Declaration.h"
 #include "nsStyleConsts.h"
 #include "nsNetUtil.h"
 #include "nsCOMPtr.h"

--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -35,16 +35,17 @@
 #include "nsQuickSort.h"
 #include "nsAttrValue.h"
 #include "nsAttrValueInlines.h"
 #include "nsAttrName.h"
 #include "nsTArray.h"
 #include "nsContentUtils.h"
 #include "nsMediaList.h"
 #include "nsCSSRules.h"
+#include "nsCSSCounterStyleRule.h"
 #include "nsCSSFontFaceRule.h"
 #include "nsStyleSet.h"
 #include "mozilla/dom/Element.h"
 #include "nsNthIndexCache.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/EventStates.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ServoStyleSet.h"

--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -1,16 +1,17 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 /* rules in a CSS stylesheet other than style rules (e.g., @import rules) */
 
 #include "nsCSSRules.h"
+#include "nsCSSCounterStyleRule.h"
 #include "nsCSSFontFaceRule.h"
 
 #include "mozilla/Attributes.h"
 
 #include "nsCSSValue.h"
 #include "mozilla/StyleSheetInlines.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/css/ImportRule.h"

--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -22,17 +22,16 @@
 #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"
 #include "nsIDOMCSSMozDocumentRule.h"
 #include "nsIDOMCSSSupportsRule.h"
 #include "nsIDOMCSSKeyframeRule.h"
 #include "nsIDOMCSSKeyframesRule.h"
 #include "nsTArray.h"
 
@@ -463,105 +462,9 @@ protected:
   virtual ~CSSSupportsRule();
 
   bool mUseGroup;
   nsString mCondition;
 };
 
 } // namespace mozilla
 
-class nsCSSCounterStyleRule final : public mozilla::css::Rule,
-                                    public nsIDOMCSSCounterStyleRule
-{
-public:
-  explicit nsCSSCounterStyleRule(nsIAtom* aName,
-                                 uint32_t aLineNumber, uint32_t aColumnNumber)
-    : mozilla::css::Rule(aLineNumber, aColumnNumber)
-    , mName(aName)
-    , mGeneration(0)
-  {
-    MOZ_ASSERT(aName, "Must have non-null name");
-  }
-
-private:
-  nsCSSCounterStyleRule(const nsCSSCounterStyleRule& aCopy);
-  ~nsCSSCounterStyleRule();
-
-public:
-  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;
-
-  // nsIDOMCSSCounterStyleRule
-  NS_DECL_NSIDOMCSSCOUNTERSTYLERULE
-
-  // WebIDL interface
-  uint16_t Type() const override;
-  void GetCssTextImpl(nsAString& aCssText) const override;
-  // The XPCOM GetName is OK
-  // The XPCOM SetName is OK
-  // The XPCOM GetSystem is OK
-  // The XPCOM SetSystem is OK
-  // The XPCOM GetSymbols is OK
-  // The XPCOM SetSymbols is OK
-  // The XPCOM GetAdditiveSymbols is OK
-  // The XPCOM SetAdditiveSymbols is OK
-  // The XPCOM GetNegative is OK
-  // The XPCOM SetNegative is OK
-  // The XPCOM GetPrefix is OK
-  // The XPCOM SetPrefix is OK
-  // The XPCOM GetSuffix is OK
-  // The XPCOM SetSuffix is OK
-  // The XPCOM GetRange is OK
-  // The XPCOM SetRange is OK
-  // The XPCOM GetPad is OK
-  // The XPCOM SetPad is OK
-  // The XPCOM GetSpeakAs is OK
-  // The XPCOM SetSpeakAs is OK
-  // The XPCOM GetFallback is OK
-  // The XPCOM SetFallback is OK
-
-  // This function is only used to check whether a non-empty value, which has
-  // been accepted by parser, is valid for the given system and descriptor.
-  static bool CheckDescValue(int32_t aSystem,
-                             nsCSSCounterDesc aDescID,
-                             const nsCSSValue& aValue);
-
-  nsIAtom* Name() const { return mName; }
-
-  uint32_t GetGeneration() const { return mGeneration; }
-
-  int32_t GetSystem() const;
-  const nsCSSValue& GetSystemArgument() const;
-
-  const nsCSSValue& GetDesc(nsCSSCounterDesc aDescID) const
-  {
-    MOZ_ASSERT(aDescID >= 0 && aDescID < eCSSCounterDesc_COUNT,
-               "descriptor ID out of range");
-    return mValues[aDescID];
-  }
-
-  void SetDesc(nsCSSCounterDesc aDescID, const nsCSSValue& aValue);
-
-  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
-
-  virtual JSObject* WrapObject(JSContext* aCx,
-                               JS::Handle<JSObject*> aGivenProto) override;
-
-private:
-  typedef decltype(&nsCSSCounterStyleRule::GetSymbols) Getter;
-  static const Getter kGetters[];
-
-  nsresult GetDescriptor(nsCSSCounterDesc aDescID, nsAString& aValue);
-  nsresult SetDescriptor(nsCSSCounterDesc aDescID, const nsAString& aValue);
-
-  nsCOMPtr<nsIAtom> mName;
-  nsCSSValue mValues[eCSSCounterDesc_COUNT];
-  uint32_t   mGeneration;
-};
-
 #endif /* !defined(nsCSSRules_h_) */