--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -142,17 +142,16 @@
 #include "nsIDOMStyleRuleChangeEvent.h"
 #include "nsIDOMStyleSheetChangeEvent.h"
 #include "nsIDOMStyleSheetApplicableStateChangeEvent.h"
 #include "nsJSUtils.h"
 #include "nsFrameLoader.h"
 #include "nsEscape.h"
 #include "nsObjectLoadingContent.h"
 #include "nsHtml5TreeOpExecutor.h"
-#include "nsIDOMElementReplaceEvent.h"
 #include "mozilla/dom/HTMLLinkElement.h"
 #include "mozilla/dom/HTMLMediaElement.h"
 #ifdef MOZ_WEBRTC
 #include "IPeerConnection.h"
 #endif // MOZ_WEBRTC
 
 #include "mozAutoDocUpdate.h"
 #include "nsGlobalWindow.h"

--- a/dom/events/EventDispatcher.cpp
+++ b/dom/events/EventDispatcher.cpp
@@ -798,18 +798,16 @@ EventDispatcher::CreateEvent(EventTarget
       aEventType.LowerCaseEqualsLiteral("timeevents"))
     return NS_NewDOMTimeEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("xulcommandevent") ||
       aEventType.LowerCaseEqualsLiteral("xulcommandevents"))
     return NS_NewDOMXULCommandEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("commandevent") ||
       aEventType.LowerCaseEqualsLiteral("commandevents"))
     return NS_NewDOMCommandEvent(aDOMEvent, aOwner, aPresContext, nullptr);
-  if (aEventType.LowerCaseEqualsLiteral("elementreplace"))
-    return NS_NewDOMElementReplaceEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("datacontainerevent") ||
       aEventType.LowerCaseEqualsLiteral("datacontainerevents"))
     return NS_NewDOMDataContainerEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("messageevent"))
     return NS_NewDOMMessageEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("notifypaintevent"))
     return NS_NewDOMNotifyPaintEvent(aDOMEvent, aOwner, aPresContext, nullptr);
   if (aEventType.LowerCaseEqualsLiteral("simplegestureevent"))

--- a/dom/events/test/test_all_synthetic_events.html
+++ b/dom/events/test/test_all_synthetic_events.html
@@ -158,20 +158,16 @@ const kEventConstructors = {
                                                                          aProps.button, aProps.relatedTarget, aProps.dataTransfer);
                                                          return e;
                                                        },
                                              },
   ErrorEvent:                                { create: function (aName, aProps) {
                                                          return new ErrorEvent(aName, aProps);
                                                        },
   },
-  ElementReplaceEvent:                       { create: function (aName, aProps) {
-                                                         return new ElementReplaceEvent(aName, aProps);
-                                                       },
-                                             },
   FocusEvent:                                { create: function (aName, aProps) {
                                                          return new FocusEvent(aName, aProps);
                                                        },
                                              },
   GamepadEvent:                              { create: function (aName, aProps) {
                                                          return new GamepadEvent(aName, aProps);
                                                        },
                                              },

--- a/dom/interfaces/events/moz.build
+++ b/dom/interfaces/events/moz.build
@@ -11,17 +11,16 @@ XPIDL_SOURCES += [
     'nsIDOMCommandEvent.idl',
     'nsIDOMCompositionEvent.idl',
     'nsIDOMCustomEvent.idl',
     'nsIDOMDataContainerEvent.idl',
     'nsIDOMDataTransfer.idl',
     'nsIDOMDeviceOrientationEvent.idl',
     'nsIDOMDOMTransactionEvent.idl',
     'nsIDOMDragEvent.idl',
-    'nsIDOMElementReplaceEvent.idl',
     'nsIDOMEvent.idl',
     'nsIDOMEventListener.idl',
     'nsIDOMEventTarget.idl',
     'nsIDOMFocusEvent.idl',
     'nsIDOMKeyEvent.idl',
     'nsIDOMMessageEvent.idl',
     'nsIDOMMouseEvent.idl',
     'nsIDOMMouseScrollEvent.idl',

deleted file mode 100644
--- a/dom/interfaces/events/nsIDOMElementReplaceEvent.idl
+++ /dev/null
@@ -1,19 +0,0 @@
-/* -*- 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/. */
-
-#include "nsIDOMEvent.idl"
-
-interface nsIDOMElement;
-
-[builtinclass, uuid(19a31767-54bf-4044-8769-cd172e37eca2)]
-interface nsIDOMElementReplaceEvent : nsIDOMEvent
-{
-  readonly attribute nsIDOMElement upgrade;
-
-  void initElementReplaceEvent(in DOMString typeArg,
-                               in boolean canBubbleArg,
-                               in boolean canCancelArg,
-                               in nsIDOMElement upgrade);
-};

--- a/dom/tests/mochitest/general/test_interfaces.html
+++ b/dom/tests/mochitest/general/test_interfaces.html
@@ -347,18 +347,16 @@ var interfaceNamesInGlobalScope =
     "DOMTransactionEvent",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "DragEvent",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "DynamicsCompressorNode",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Element",
 // IMPORTANT: Do not change this list without review from a DOM peer!
-    "ElementReplaceEvent",
-// IMPORTANT: Do not change this list without review from a DOM peer!
     "ErrorEvent",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "Event",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventSource",
 // IMPORTANT: Do not change this list without review from a DOM peer!
     "EventTarget",
 // IMPORTANT: Do not change this list without review from a DOM peer!

deleted file mode 100644
--- a/dom/webidl/ElementReplaceEvent.webidl
+++ /dev/null
@@ -1,23 +0,0 @@
-/* -*- 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/.
- */
-
-[Constructor(DOMString type, optional ElementReplaceEventInit eventInitDict), HeaderFile="GeneratedEventClasses.h"]
-interface ElementReplaceEvent : Event
-{
-  readonly attribute Element? upgrade;
-
-  // initElementReplaceEvent is a Gecko specific deprecated method.
-  [Throws]
-  void initElementReplaceEvent(DOMString type,
-                               boolean canBubble,
-                               boolean cancelable,
-                               Element? upgrade);
-};
-
-dictionary ElementReplaceEventInit : EventInit
-{
-  Element? upgrade = null;
-};

--- a/dom/webidl/moz.build
+++ b/dom/webidl/moz.build
@@ -530,17 +530,16 @@ if CONFIG['MOZ_GAMEPAD']:
     ]
 
 WEBIDL_FILES += [
     'CloseEvent.webidl',
     'CustomEvent.webidl',
     'DeviceOrientationEvent.webidl',
     'DeviceStorageChangeEvent.webidl',
     'DOMTransactionEvent.webidl',
-    'ElementReplaceEvent.webidl',
     'HashChangeEvent.webidl',
     'MozApplicationEvent.webidl',
     'MozSettingsEvent.webidl',
     'PageTransitionEvent.webidl',
     'PopStateEvent.webidl',
     'PopupBlockedEvent.webidl',
     'ProgressEvent.webidl',
     'RecordErrorEvent.webidl',

--- a/js/xpconnect/src/event_impl_gen.conf.in
+++ b/js/xpconnect/src/event_impl_gen.conf.in
@@ -14,17 +14,16 @@ simple_events = [
     'DOMTransactionEvent',
     'PopStateEvent',
     'DeviceOrientationEvent',
     'MozApplicationEvent',
     'SmartCardEvent',
     'StyleRuleChangeEvent',
     'StyleSheetChangeEvent',
     'StyleSheetApplicableStateChangeEvent',
-    'ElementReplaceEvent',
 #ifdef MOZ_WEBSPEECH
     'SpeechSynthesisEvent',
 #endif
     'DeviceStorageChangeEvent',
     'PopupBlockedEvent',
     'RecordErrorEvent',
 #ifdef MOZ_WEBSPEECH
     'SpeechRecognitionEvent',

--- a/xpcom/reflect/xptinfo/ShimInterfaceInfo.cpp
+++ b/xpcom/reflect/xptinfo/ShimInterfaceInfo.cpp
@@ -38,17 +38,16 @@
 #include "nsIDOMDOMRequest.h"
 #include "nsIDOMDOMTransactionEvent.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMDocumentFragment.h"
 #include "nsIDOMDocumentType.h"
 #include "nsIDOMDocumentXBL.h"
 #include "nsIDOMDragEvent.h"
 #include "nsIDOMElement.h"
-#include "nsIDOMElementReplaceEvent.h"
 #include "nsIDOMEvent.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIDOMFileList.h"
 #include "nsIDOMFileReader.h"
 #include "nsIDOMFocusEvent.h"
 #include "nsIDOMFormData.h"
 #include "nsIDOMGeoPositionError.h"
 #include "nsIDOMHistory.h"
@@ -196,17 +195,16 @@
 #include "mozilla/dom/DOMRequestBinding.h"
 #include "mozilla/dom/DOMTransactionEventBinding.h"
 #include "mozilla/dom/DocumentBinding.h"
 #include "mozilla/dom/DocumentFragmentBinding.h"
 #include "mozilla/dom/DocumentTypeBinding.h"
 #include "mozilla/dom/DocumentBinding.h"
 #include "mozilla/dom/DragEventBinding.h"
 #include "mozilla/dom/ElementBinding.h"
-#include "mozilla/dom/ElementReplaceEventBinding.h"
 #include "mozilla/dom/EventBinding.h"
 #include "mozilla/dom/EventTargetBinding.h"
 #include "mozilla/dom/FileListBinding.h"
 #include "mozilla/dom/FileReaderBinding.h"
 #include "mozilla/dom/FocusEventBinding.h"
 #include "mozilla/dom/FormDataBinding.h"
 #include "mozilla/dom/HistoryBinding.h"
 #include "mozilla/dom/HTMLAnchorElementBinding.h"
@@ -404,17 +402,16 @@ const ComponentsInterfaceShimEntry kComp
   DEFINE_SHIM(DOMRequest),
   DEFINE_SHIM(DOMTransactionEvent),
   DEFINE_SHIM(Document),
   DEFINE_SHIM(DocumentFragment),
   DEFINE_SHIM(DocumentType),
   DEFINE_SHIM_WITH_CUSTOM_INTERFACE(nsIDOMDocumentXBL, Document),
   DEFINE_SHIM(DragEvent),
   DEFINE_SHIM(Element),
-  DEFINE_SHIM(ElementReplaceEvent),
   DEFINE_SHIM(Event),
   DEFINE_SHIM(EventTarget),
   DEFINE_SHIM(FileReader),
   DEFINE_SHIM(FileList),
   DEFINE_SHIM(FocusEvent),
   DEFINE_SHIM(FormData),
   DEFINE_SHIM_WITH_CUSTOM_INTERFACE(nsIDOMGeoPositionError, PositionError),
   DEFINE_SHIM(History),