--- a/layout/inspector/InspectorUtils.cpp
+++ b/layout/inspector/InspectorUtils.cpp
@@ -19,17 +19,16 @@
 #include "nsIDOMElement.h"
 #include "nsIDocument.h"
 #include "nsIPresShell.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMCharacterData.h"
 #include "nsRuleNode.h"
 #include "nsIStyleRule.h"
 #include "mozilla/css/StyleRule.h"
-#include "nsICSSStyleRuleDOMWrapper.h"
 #include "nsIDOMWindow.h"
 #include "nsXBLBinding.h"
 #include "nsXBLPrototypeBinding.h"
 #include "nsIMutableArray.h"
 #include "nsBindingManager.h"
 #include "ChildIterator.h"
 #include "nsComputedDOMStyle.h"
 #include "mozilla/EventStateManager.h"

--- a/layout/style/ServoStyleRule.cpp
+++ b/layout/style/ServoStyleRule.cpp
@@ -120,23 +120,17 @@ ServoStyleRuleDeclaration::GetServoCSSPa
 ServoStyleRule::ServoStyleRule(already_AddRefed<RawServoStyleRule> aRawRule,
                                uint32_t aLine, uint32_t aColumn)
   : BindingStyleRule(aLine, aColumn)
   , mRawRule(aRawRule)
   , mDecls(Servo_StyleRule_GetStyle(mRawRule).Consume())
 {
 }
 
-// QueryInterface implementation for ServoStyleRule
-NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ServoStyleRule)
-  NS_INTERFACE_MAP_ENTRY(nsICSSStyleRuleDOMWrapper)
-NS_INTERFACE_MAP_END_INHERITING(css::Rule)
-
-NS_IMPL_ADDREF_INHERITED(ServoStyleRule, css::Rule)
-NS_IMPL_RELEASE_INHERITED(ServoStyleRule, css::Rule)
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(ServoStyleRule, css::Rule)
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(ServoStyleRule)
 
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(ServoStyleRule, css::Rule)
   // Keep this in sync with IsCCLeaf.
 
   // Trace the wrapper for our declaration.  This just expands out
   // NS_IMPL_CYCLE_COLLECTION_TRACE_PRESERVED_WRAPPER which we can't use
@@ -198,25 +192,16 @@ ServoStyleRule::List(FILE* out, int32_t 
   for (int32_t i = 0; i < aIndent; i++) {
     str.AppendLiteral("  ");
   }
   Servo_StyleRule_Debug(mRawRule, &str);
   fprintf_stderr(out, "%s\n", str.get());
 }
 #endif
 
-/* nsICSSStyleRuleDOMWrapper implementation */
-
-NS_IMETHODIMP
-ServoStyleRule::GetCSSStyleRule(BindingStyleRule **aResult)
-{
-  NS_ADDREF(*aResult = this);
-  return NS_OK;
-}
-
 /* CSSRule implementation */
 
 uint16_t
 ServoStyleRule::Type() const
 {
   return CSSRuleBinding::STYLE_RULE;
 }
 

--- a/layout/style/ServoStyleRule.h
+++ b/layout/style/ServoStyleRule.h
@@ -8,18 +8,16 @@
 
 #ifndef mozilla_ServoStyleRule_h
 #define mozilla_ServoStyleRule_h
 
 #include "mozilla/BindingStyleRule.h"
 #include "mozilla/ServoBindingTypes.h"
 #include "mozilla/WeakPtr.h"
 
-#include "nsICSSStyleRuleDOMWrapper.h"
-#include "nsICSSStyleRuleDOMWrapper.h"
 #include "nsDOMCSSDeclaration.h"
 
 namespace mozilla {
 
 namespace dom {
 class DocGroup;
 } // namespace dom
 
@@ -54,33 +52,29 @@ private:
 
   inline ServoStyleRule* Rule();
   inline const ServoStyleRule* Rule() const;
 
   RefPtr<ServoDeclarationBlock> mDecls;
 };
 
 class ServoStyleRule final : public BindingStyleRule
-                           , public nsICSSStyleRuleDOMWrapper
                            , public SupportsWeakPtr<ServoStyleRule>
 {
 public:
   ServoStyleRule(already_AddRefed<RawServoStyleRule> aRawRule,
                  uint32_t aLine, uint32_t aColumn);
 
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(ServoStyleRule,
                                                          css::Rule)
   bool IsCCLeaf() const final MOZ_MUST_OVERRIDE;
 
   MOZ_DECLARE_WEAKREFERENCE_TYPENAME(ServoStyleRule)
 
-  // nsICSSStyleRuleDOMWrapper
-  NS_IMETHOD GetCSSStyleRule(BindingStyleRule **aResult) override;
-
   uint32_t GetSelectorCount() override;
   nsresult GetSelectorText(uint32_t aSelectorIndex,
                            nsAString& aText) override;
   nsresult GetSpecificity(uint32_t aSelectorIndex,
                           uint64_t* aSpecificity) override;
   nsresult SelectorMatchesElement(dom::Element* aElement,
                                   uint32_t aSelectorIndex,
                                   const nsAString& aPseudo,

--- a/layout/style/StyleRule.cpp
+++ b/layout/style/StyleRule.cpp
@@ -1189,24 +1189,16 @@ nsICSSDeclaration*
 StyleRule::Style()
 {
   if (!mDOMDeclaration) {
     mDOMDeclaration.reset(new DOMCSSDeclarationImpl(this));
   }
   return mDOMDeclaration.get();
 }
 
-NS_IMETHODIMP
-StyleRule::GetCSSStyleRule(BindingStyleRule **aResult)
-{
-  *aResult = this;
-  NS_ADDREF(*aResult);
-  return NS_OK;
-}
-
 StyleRule::StyleRule(nsCSSSelectorList* aSelector,
                      Declaration* aDeclaration,
                      uint32_t aLineNumber,
                      uint32_t aColumnNumber)
   : BindingStyleRule(aLineNumber, aColumnNumber),
     mSelector(aSelector),
     mDeclaration(aDeclaration)
 {
@@ -1242,17 +1234,16 @@ StyleRule::DropReferences()
 // QueryInterface implementation for StyleRule
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(StyleRule)
   if (aIID.Equals(NS_GET_IID(mozilla::css::StyleRule))) {
     *aInstancePtr = this;
     NS_ADDREF_THIS();
     return NS_OK;
   }
   else
-  NS_INTERFACE_MAP_ENTRY(nsICSSStyleRuleDOMWrapper)
 NS_INTERFACE_MAP_END_INHERITING(Rule)
 
 NS_IMPL_ADDREF_INHERITED(StyleRule, Rule)
 NS_IMPL_RELEASE_INHERITED(StyleRule, Rule)
 
 NS_IMPL_CYCLE_COLLECTION_CLASS(StyleRule)
 NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(StyleRule, Rule)
   // Keep this in sync with IsCCLeaf.

--- a/layout/style/StyleRule.h
+++ b/layout/style/StyleRule.h
@@ -17,17 +17,16 @@
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StyleSetHandle.h"
 #include "mozilla/UniquePtr.h"
 
 #include "nsString.h"
 #include "nsCOMPtr.h"
 #include "nsCSSPseudoElements.h"
 #include "nsIStyleRule.h"
-#include "nsICSSStyleRuleDOMWrapper.h"
 
 class nsAtom;
 struct nsCSSSelectorList;
 
 namespace mozilla {
 enum class CSSPseudoClassType : uint8_t;
 class CSSStyleSheet;
 } // namespace mozilla
@@ -313,35 +312,31 @@ private:
 class DOMCSSDeclarationImpl;
 
 namespace mozilla {
 namespace css {
 
 class Declaration;
 
 class StyleRule final : public BindingStyleRule
-                      , public nsICSSStyleRuleDOMWrapper
 {
  public:
   StyleRule(nsCSSSelectorList* aSelector,
             Declaration *aDeclaration,
             uint32_t aLineNumber, uint32_t aColumnNumber);
 private:
   // for |Clone|
   StyleRule(const StyleRule& aCopy);
 public:
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_CSS_STYLE_RULE_IMPL_CID)
 
   NS_DECL_ISUPPORTS_INHERITED
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(StyleRule, Rule)
   bool IsCCLeaf() const override;
 
-  // nsICSSStyleRuleDOMWrapper
-  NS_IMETHOD GetCSSStyleRule(BindingStyleRule **aResult) override;
-
   uint32_t GetSelectorCount() override;
   nsresult GetSelectorText(uint32_t aSelectorIndex,
                                    nsAString& aText) override;
   nsresult GetSpecificity(uint32_t aSelectorIndex,
                           uint64_t* aSpecificity) override;
   nsresult SelectorMatchesElement(dom::Element* aElement,
                                   uint32_t aSelectorIndex,
                                   const nsAString& aPseudo,

--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -50,17 +50,16 @@ EXPORTS += [
     'nsCSSRuleProcessor.h',
     'nsCSSScanner.h',
     'nsCSSValue.h',
     'nsDOMCSSAttrDeclaration.h',
     'nsDOMCSSDeclaration.h',
     'nsDOMCSSRGBColor.h',
     'nsICSSDeclaration.h',
     'nsICSSLoaderObserver.h',
-    'nsICSSStyleRuleDOMWrapper.h',
     'nsIStyleRule.h',
     'nsIStyleRuleProcessor.h',
     'nsLayoutStylesheetCache.h',
     'nsMediaFeatures.h',
     'nsMediaList.h',
     'nsRuleData.h',
     'nsRuleNode.h',
     'nsRuleProcessorData.h',

deleted file mode 100644
--- a/layout/style/nsICSSStyleRuleDOMWrapper.h
+++ /dev/null
@@ -1,34 +0,0 @@
-/* -*- 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/. */
-
-/*
- * interface to provide DOM inspector with access to internal interfaces
- * via DOM interface
- */
-
-#ifndef nsICSSStyleRuleDOMWrapper_h_
-#define nsICSSStyleRuleDOMWrapper_h_
-
-// IID for the nsICSSStyleRuleDOMWrapper interface
-// {cee1bbb6-0a32-4cf3-8d42-ba3938e9ecaa}
-#define NS_ICSS_STYLE_RULE_DOM_WRAPPER_IID \
-{0xcee1bbb6, 0x0a32, 0x4cf3, {0x8d, 0x42, 0xba, 0x39, 0x38, 0xe9, 0xec, 0xaa}}
-
-namespace mozilla {
-class BindingStyleRule;
-} // namespace mozilla
-
-class nsICSSStyleRuleDOMWrapper : public nsISupports {
-public:
-  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ICSS_STYLE_RULE_DOM_WRAPPER_IID)
-
-  NS_IMETHOD GetCSSStyleRule(mozilla::BindingStyleRule** aResult) = 0;
-};
-
-NS_DEFINE_STATIC_IID_ACCESSOR(nsICSSStyleRuleDOMWrapper,
-                              NS_ICSS_STYLE_RULE_DOM_WRAPPER_IID)
-
-#endif /* !defined(nsICSSStyleRuleDOMWrapper_h_) */