--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -69,17 +69,16 @@
 #include "nsIDOMEventTarget.h"
 
 // CSS related includes
 #include "nsCSSRules.h"
 #include "nsIDOMCSSRule.h"
 #include "nsMemory.h"
 
 // includes needed for the prototype chain interfaces
-#include "nsIDOMCSSKeyframesRule.h"
 #include "nsIDOMCSSCounterStyleRule.h"
 #include "nsIDOMXULCommandDispatcher.h"
 #include "nsIControllers.h"
 #ifdef MOZ_XUL
 #include "nsITreeSelection.h"
 #include "nsITreeContentView.h"
 #include "nsITreeView.h"
 #include "nsIXULTemplateBuilder.h"
@@ -214,20 +213,16 @@ static nsDOMClassInfoData sClassInfoData
                                        nsIXPCScriptable::WANT_ENUMERATE |
                                        nsIXPCScriptable::IS_GLOBAL_OBJECT)
   NS_DEFINE_CHROME_ONLY_CLASSINFO_DATA(ChromeMessageBroadcaster, nsDOMGenericSH,
                                        DOM_DEFAULT_SCRIPTABLE_FLAGS)
   NS_DEFINE_CHROME_ONLY_CLASSINFO_DATA(ChromeMessageSender, nsDOMGenericSH,
                                        DOM_DEFAULT_SCRIPTABLE_FLAGS)
 
 
-  NS_DEFINE_CLASSINFO_DATA(CSSKeyframesRule, nsCSSRuleSH,
-                           DOM_DEFAULT_SCRIPTABLE_FLAGS |
-                           nsIXPCScriptable::WANT_PRECREATE)
-
   NS_DEFINE_CLASSINFO_DATA(CSSCounterStyleRule, nsCSSRuleSH,
                            DOM_DEFAULT_SCRIPTABLE_FLAGS |
                            nsIXPCScriptable::WANT_PRECREATE)
 
   NS_DEFINE_CHROME_XBL_CLASSINFO_DATA(XULControlElement, nsDOMGenericSH,
                                       DOM_DEFAULT_SCRIPTABLE_FLAGS)
   NS_DEFINE_CHROME_XBL_CLASSINFO_DATA(XULLabeledControlElement, nsDOMGenericSH,
                                       DOM_DEFAULT_SCRIPTABLE_FLAGS)
@@ -537,21 +532,16 @@ nsDOMClassInfo::Init()
 
   DOM_CLASSINFO_MAP_BEGIN_NO_CLASS_IF(ChromeMessageSender, nsISupports)
     DOM_CLASSINFO_MAP_ENTRY(nsIFrameScriptLoader)
     DOM_CLASSINFO_MAP_ENTRY(nsIProcessScriptLoader)
     DOM_CLASSINFO_MAP_ENTRY(nsIMessageListenerManager)
     DOM_CLASSINFO_MAP_ENTRY(nsIMessageSender)
   DOM_CLASSINFO_MAP_END
 
-  DOM_CLASSINFO_MAP_BEGIN(CSSKeyframesRule, nsIDOMCSSKeyframesRule)
-    DOM_CLASSINFO_MAP_ENTRY(nsIDOMCSSRule)
-    DOM_CLASSINFO_MAP_ENTRY(nsIDOMCSSKeyframesRule)
-  DOM_CLASSINFO_MAP_END
-
   DOM_CLASSINFO_MAP_BEGIN(CSSCounterStyleRule, nsIDOMCSSCounterStyleRule)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMCSSRule)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMCSSCounterStyleRule)
   DOM_CLASSINFO_MAP_END
 
   DOM_CLASSINFO_MAP_BEGIN_NO_CLASS_IF(XULControlElement, nsIDOMXULControlElement)
     DOM_CLASSINFO_MAP_ENTRY(nsIDOMXULControlElement)
   DOM_CLASSINFO_MAP_END

--- a/dom/base/nsDOMClassInfoID.h
+++ b/dom/base/nsDOMClassInfoID.h
@@ -34,18 +34,16 @@ enum nsDOMClassInfoID
   eDOMClassInfo_XULTreeBuilder_id,
 #endif
 
   eDOMClassInfo_ContentFrameMessageManager_id,
   eDOMClassInfo_ContentProcessMessageManager_id,
   eDOMClassInfo_ChromeMessageBroadcaster_id,
   eDOMClassInfo_ChromeMessageSender_id,
 
-  eDOMClassInfo_CSSKeyframesRule_id,
-
   // @counter-style in CSS
   eDOMClassInfo_CSSCounterStyleRule_id,
 
   eDOMClassInfo_XULControlElement_id,
   eDOMClassInfo_XULLabeledControlElement_id,
   eDOMClassInfo_XULButtonElement_id,
   eDOMClassInfo_XULCheckboxElement_id,
   eDOMClassInfo_XULPopupElement_id,

--- a/dom/base/nsWrapperCache.h
+++ b/dom/base/nsWrapperCache.h
@@ -18,17 +18,16 @@ namespace mozilla {
 namespace dom {
 class TabChildGlobal;
 class ProcessGlobal;
 } // namespace dom
 } // namespace mozilla
 class SandboxPrivate;
 class nsInProcessTabChildGlobal;
 class nsWindowRoot;
-class nsCSSKeyframesRule;
 class nsCSSCounterStyleRule;
 
 #define NS_WRAPPERCACHE_IID \
 { 0x6f3179a1, 0x36f7, 0x4a5c, \
   { 0x8c, 0xf1, 0xad, 0xc8, 0x7c, 0xde, 0x3e, 0x87 } }
 
 /**
  * Class to store the wrapper for an object. This can only be used with objects
@@ -277,17 +276,16 @@ private:
   // Friend declarations for things that need to be able to call
   // SetIsNotDOMBinding().  The goal is to get rid of all of these, and
   // SetIsNotDOMBinding() too.
   friend class mozilla::dom::TabChildGlobal;
   friend class mozilla::dom::ProcessGlobal;
   friend class SandboxPrivate;
   friend class nsInProcessTabChildGlobal;
   friend class nsWindowRoot;
-  friend class nsCSSKeyframesRule;
   friend class nsCSSCounterStyleRule;
   void SetIsNotDOMBinding()
   {
     MOZ_ASSERT(!mWrapper && !(GetWrapperFlags() & ~WRAPPER_IS_NOT_DOM_BINDING),
                "This flag should be set before creating any wrappers.");
     SetWrapperFlags(WRAPPER_IS_NOT_DOM_BINDING);
   }
 

--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -221,16 +221,21 @@ DOMInterfaces = {
     'nativeType': 'mozilla::css::ImportRule',
 },
 
 'CSSKeyframeRule': {
     'nativeType': 'nsCSSKeyframeRule',
     'headerFile': 'nsCSSRules.h',
 },
 
+'CSSKeyframesRule': {
+    'nativeType': 'nsCSSKeyframesRule',
+    'headerFile': 'nsCSSRules.h',
+},
+
 'CSSLexer': {
     'wrapperCache': False
 },
 
 'CSSMediaRule': {
     'nativeType': 'mozilla::css::MediaRule',
     'headerFile': 'nsCSSRules.h',
 },

new file mode 100644
--- /dev/null
+++ b/dom/webidl/CSSKeyframesRule.webidl
@@ -0,0 +1,18 @@
+/* -*- Mode: IDL; 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/.
+ *
+ * The origin of this IDL file is
+ * https://drafts.csswg.org/css-animations/#interface-csskeyframesrule
+ */
+
+// https://drafts.csswg.org/css-animations/#interface-csskeyframesrule
+interface CSSKeyframesRule : CSSRule {
+           attribute DOMString   name;
+  readonly attribute CSSRuleList cssRules;
+
+  void            appendRule(DOMString rule);
+  void            deleteRule(DOMString select);
+  CSSKeyframeRule? findRule(DOMString select);
+};

--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -90,16 +90,17 @@ WEBIDL_FILES = [
     'CSS.webidl',
     'CSSAnimation.webidl',
     'CSSConditionRule.webidl',
     'CSSFontFaceRule.webidl',
     'CSSFontFeatureValuesRule.webidl',
     'CSSGroupingRule.webidl',
     'CSSImportRule.webidl',
     'CSSKeyframeRule.webidl',
+    'CSSKeyframesRule.webidl',
     'CSSLexer.webidl',
     'CSSMediaRule.webidl',
     'CSSMozDocumentRule.webidl',
     'CSSNamespaceRule.webidl',
     'CSSPageRule.webidl',
     'CSSPrimitiveValue.webidl',
     'CSSPseudoElement.webidl',
     'CSSRule.webidl',

--- a/layout/style/nsCSSRules.cpp
+++ b/layout/style/nsCSSRules.cpp
@@ -37,16 +37,17 @@
 #include "mozilla/dom/CSSImportRuleBinding.h"
 #include "mozilla/dom/CSSMediaRuleBinding.h"
 #include "mozilla/dom/CSSSupportsRuleBinding.h"
 #include "mozilla/dom/CSSMozDocumentRuleBinding.h"
 #include "mozilla/dom/CSSPageRuleBinding.h"
 #include "mozilla/dom/CSSFontFaceRuleBinding.h"
 #include "mozilla/dom/CSSFontFeatureValuesRuleBinding.h"
 #include "mozilla/dom/CSSKeyframeRuleBinding.h"
+#include "mozilla/dom/CSSKeyframesRuleBinding.h"
 #include "StyleRule.h"
 #include "nsFont.h"
 #include "nsIURI.h"
 #include "mozAutoDocUpdate.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
 
@@ -2203,17 +2204,16 @@ nsCSSKeyframeRule::WrapObject(JSContext*
 
 nsCSSKeyframesRule::nsCSSKeyframesRule(const nsCSSKeyframesRule& aCopy)
   // copy everything except our reference count.  GroupRule's copy
   // constructor also doesn't copy the lazily-constructed
   // mRuleCollection.
   : GroupRule(aCopy),
     mName(aCopy.mName)
 {
-  SetIsNotDOMBinding();
 }
 
 nsCSSKeyframesRule::~nsCSSKeyframesRule()
 {
 }
 
 /* virtual */ already_AddRefed<css::Rule>
 nsCSSKeyframesRule::Clone() const
@@ -2223,17 +2223,16 @@ nsCSSKeyframesRule::Clone() const
 }
 
 NS_IMPL_ADDREF_INHERITED(nsCSSKeyframesRule, css::GroupRule)
 NS_IMPL_RELEASE_INHERITED(nsCSSKeyframesRule, css::GroupRule)
 
 // QueryInterface implementation for nsCSSKeyframesRule
 NS_INTERFACE_MAP_BEGIN(nsCSSKeyframesRule)
   NS_INTERFACE_MAP_ENTRY(nsIDOMCSSKeyframesRule)
-  NS_DOM_INTERFACE_MAP_ENTRY_CLASSINFO(CSSKeyframesRule)
 NS_INTERFACE_MAP_END_INHERITING(GroupRule)
 
 #ifdef DEBUG
 void
 nsCSSKeyframesRule::List(FILE* out, int32_t aIndent) const
 {
   nsAutoCString indentStr;
   for (int32_t indent = aIndent; --indent >= 0; ) {
@@ -2384,23 +2383,28 @@ nsCSSKeyframesRule::DeleteRule(const nsA
   }
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsCSSKeyframesRule::FindRule(const nsAString& aKey,
                              nsIDOMCSSKeyframeRule** aResult)
 {
+  NS_IF_ADDREF(*aResult = FindRule(aKey));
+  return NS_OK;
+}
+
+nsCSSKeyframeRule*
+nsCSSKeyframesRule::FindRule(const nsAString& aKey)
+{
   uint32_t index = FindRuleIndexForKey(aKey);
   if (index == RULE_NOT_FOUND) {
-    *aResult = nullptr;
-  } else {
-    NS_ADDREF(*aResult = static_cast<nsCSSKeyframeRule*>(mRules[index]));
+    return nullptr;
   }
-  return NS_OK;
+  return static_cast<nsCSSKeyframeRule*>(mRules[index]);
 }
 
 // GroupRule interface
 /* virtual */ bool
 nsCSSKeyframesRule::UseForPresentation(nsPresContext* aPresContext,
                                        nsMediaQueryResultCacheKey& aKey)
 {
   MOZ_ASSERT(false, "should not be called");
@@ -2419,18 +2423,17 @@ nsCSSKeyframesRule::SizeOfIncludingThis(
 
   return n;
 }
 
 /* virtual */ JSObject*
 nsCSSKeyframesRule::WrapObject(JSContext* aCx,
                                JS::Handle<JSObject*> aGivenProto)
 {
-  NS_NOTREACHED("We called SetIsNotDOMBinding() in our constructor");
-  return nullptr;
+  return CSSKeyframesRuleBinding::Wrap(aCx, this, aGivenProto);
 }
 
 // -------------------------------------------
 // nsCSSPageStyleDeclaration
 //
 
 nsCSSPageStyleDeclaration::nsCSSPageStyleDeclaration(nsCSSPageRule* aRule)
   : mRule(aRule)

--- a/layout/style/nsCSSRules.h
+++ b/layout/style/nsCSSRules.h
@@ -464,17 +464,16 @@ class nsCSSKeyframesRule final : public 
                                  public nsIDOMCSSKeyframesRule
 {
 public:
   nsCSSKeyframesRule(const nsSubstring& aName,
                      uint32_t aLineNumber, uint32_t aColumnNumber)
     : mozilla::css::GroupRule(aLineNumber, aColumnNumber)
     , mName(aName)
   {
-    SetIsNotDOMBinding();
   }
 private:
   nsCSSKeyframesRule(const nsCSSKeyframesRule& aCopy);
   ~nsCSSKeyframesRule();
 public:
   NS_DECL_ISUPPORTS_INHERITED
 
   // Rule methods
@@ -486,16 +485,22 @@ public:
   virtual already_AddRefed<mozilla::css::Rule> Clone() const override;
 
   // nsIDOMCSSKeyframesRule interface
   NS_DECL_NSIDOMCSSKEYFRAMESRULE
 
   // WebIDL interface
   uint16_t Type() const override;
   void GetCssTextImpl(nsAString& aCssText) const override;
+  // The XPCOM GetName is OK
+  // The XPCOM SetName is OK
+  using mozilla::css::GroupRule::CssRules;
+  // The XPCOM appendRule is OK, since it never throws
+  // The XPCOM deleteRule is OK, since it never throws
+  nsCSSKeyframeRule* FindRule(const nsAString& aKey);
 
   // rest of GroupRule
   virtual bool UseForPresentation(nsPresContext* aPresContext,
                                     nsMediaQueryResultCacheKey& aKey) override;
 
   const nsString& GetName() { return mName; }
 
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;