--- a/content/base/public/nsIXMLHttpRequest.idl
+++ b/content/base/public/nsIXMLHttpRequest.idl
@@ -16,37 +16,16 @@ interface nsPIDOMWindow;
 interface nsIInputStream;
 interface nsIDOMBlob;
 
 %{C++
 // for jsval
 #include "jsapi.h"
 %}
 
-/**
- * Parameters for instantiating an XMLHttpRequest. They are passed as an
- * optional argument to the constructor:
- *
- *  new XMLHttpRequest({anon: true, system: true});
- *
- */
-dictionary XMLHttpRequestParameters
-{
-  /**
-   * If true, the request will be sent without cookie and authentication
-   * headers.
-   */
-  boolean mozAnon;
-
-  /**
-   * If true, the same origin policy will not be enforced on the request.
-   */
-  boolean mozSystem;
-};
-
 [scriptable, builtinclass, uuid(a137d5e6-81e2-4fa3-a791-26459df723ff)]
 interface nsIXMLHttpRequestEventTarget : nsIDOMEventTarget {
   // event handler attributes
   [implicit_jscontext] attribute jsval onabort;
   [implicit_jscontext] attribute jsval onerror;
   [implicit_jscontext] attribute jsval onload;
   [implicit_jscontext] attribute jsval onloadstart;
   [implicit_jscontext] attribute jsval onprogress;

--- a/content/base/src/nsXMLHttpRequest.cpp
+++ b/content/base/src/nsXMLHttpRequest.cpp
@@ -465,53 +465,16 @@ nsXMLHttpRequest::Init(nsIPrincipal* aPr
                "Expecting an outer window here!");
   NS_ENSURE_ARG_POINTER(aPrincipal);
   Construct(aPrincipal,
             aOwnerWindow ? aOwnerWindow->GetCurrentInnerWindow() : nullptr,
             aBaseURI);
   return NS_OK;
 }
 
-/**
- * This Initialize method is called from XPConnect via nsIJSNativeInitializer.
- */
-NS_IMETHODIMP
-nsXMLHttpRequest::Initialize(nsISupports* aOwner, JSContext* cx, JSObject* obj,
-                             uint32_t argc, jsval *argv)
-{
-  nsCOMPtr<nsPIDOMWindow> owner = do_QueryInterface(aOwner);
-  if (!owner) {
-    NS_WARNING("Unexpected nsIJSNativeInitializer owner");
-    return NS_OK;
-  }
-
-  // This XHR object is bound to a |window|,
-  // so re-set principal and script context.
-  nsCOMPtr<nsIScriptObjectPrincipal> scriptPrincipal = do_QueryInterface(aOwner);
-  NS_ENSURE_STATE(scriptPrincipal);
-
-  Construct(scriptPrincipal->GetPrincipal(), owner);
-  if (argc) {
-    nsresult rv = InitParameters(cx, argv);
-    NS_ENSURE_SUCCESS(rv, rv);
-  }
-  return NS_OK;
-}
-
-nsresult
-nsXMLHttpRequest::InitParameters(JSContext* aCx, const jsval* aParams)
-{
-  mozilla::idl::XMLHttpRequestParameters params;
-  nsresult rv = params.Init(aCx, aParams);
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  InitParameters(params.mozAnon, params.mozSystem);
-  return NS_OK;
-}
-
 void
 nsXMLHttpRequest::InitParameters(bool aAnon, bool aSystem)
 {
   if (!aAnon && !aSystem) {
     return;
   }
 
   // Check for permissions.
@@ -633,17 +596,16 @@ NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_
   NS_INTERFACE_MAP_ENTRY(nsIXMLHttpRequest)
   NS_INTERFACE_MAP_ENTRY(nsIJSXMLHttpRequest)
   NS_INTERFACE_MAP_ENTRY(nsIRequestObserver)
   NS_INTERFACE_MAP_ENTRY(nsIStreamListener)
   NS_INTERFACE_MAP_ENTRY(nsIChannelEventSink)
   NS_INTERFACE_MAP_ENTRY(nsIProgressEventSink)
   NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
   NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
-  NS_INTERFACE_MAP_ENTRY(nsIJSNativeInitializer)
   NS_INTERFACE_MAP_ENTRY(nsITimerCallback)
   NS_INTERFACE_MAP_ENTRY(nsISizeOfEventTarget)
 NS_INTERFACE_MAP_END_INHERITING(nsXHREventTarget)
 
 NS_IMPL_ADDREF_INHERITED(nsXMLHttpRequest, nsXHREventTarget)
 NS_IMPL_RELEASE_INHERITED(nsXMLHttpRequest, nsXHREventTarget)
 
 NS_IMPL_EVENT_HANDLER(nsXMLHttpRequest, readystatechange)

--- a/content/base/src/nsXMLHttpRequest.h
+++ b/content/base/src/nsXMLHttpRequest.h
@@ -21,17 +21,16 @@
 #include "nsIChannelEventSink.h"
 #include "nsIAsyncVerifyRedirectCallback.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIHttpHeaderVisitor.h"
 #include "nsIProgressEventSink.h"
 #include "nsCOMArray.h"
 #include "nsJSUtils.h"
 #include "nsTArray.h"
-#include "nsIJSNativeInitializer.h"
 #include "nsIDOMLSProgressEvent.h"
 #include "nsITimer.h"
 #include "nsIDOMProgressEvent.h"
 #include "nsDOMEventTargetHelper.h"
 #include "nsDOMFile.h"
 #include "nsDOMBlobBuilder.h"
 #include "nsIPrincipal.h"
 #include "nsIScriptObjectPrincipal.h"
@@ -119,17 +118,16 @@ class nsXMLHttpRequestXPCOMifier;
 class nsXMLHttpRequest : public nsXHREventTarget,
                          public nsIXMLHttpRequest,
                          public nsIJSXMLHttpRequest,
                          public nsIStreamListener,
                          public nsIChannelEventSink,
                          public nsIProgressEventSink,
                          public nsIInterfaceRequestor,
                          public nsSupportsWeakReference,
-                         public nsIJSNativeInitializer,
                          public nsITimerCallback,
                          public nsISizeOfEventTarget
 {
   friend class nsXHRParseEndListener;
   friend class nsXMLHttpRequestXPCOMifier;
 
 public:
   nsXMLHttpRequest();
@@ -188,18 +186,16 @@ public:
   {
     MOZ_ASSERT(aPrincipal);
     MOZ_ASSERT_IF(aOwnerWindow, aOwnerWindow->IsInnerWindow());
     mPrincipal = aPrincipal;
     BindToOwner(aOwnerWindow);
     mBaseURI = aBaseURI;
   }
 
-  // Initialize XMLHttpRequestParameter object.
-  nsresult InitParameters(JSContext* aCx, const jsval* aParams);
   void InitParameters(bool aAnon, bool aSystem);
 
   void SetParameters(bool aAnon, bool aSystem)
   {
     mIsAnon = aAnon;
     mIsSystem = aSystem;
   }
 
@@ -223,20 +219,16 @@ public:
   NS_DECL_NSIPROGRESSEVENTSINK
 
   // nsIInterfaceRequestor
   NS_DECL_NSIINTERFACEREQUESTOR
 
   // nsITimerCallback
   NS_DECL_NSITIMERCALLBACK
 
-  // nsIJSNativeInitializer
-  NS_IMETHOD Initialize(nsISupports* aOwner, JSContext* cx, JSObject* obj,
-                       uint32_t argc, jsval* argv);
-
   // nsISizeOfEventTarget
   virtual size_t
     SizeOfEventTargetIncludingThis(nsMallocSizeOfFun aMallocSizeOf) const;
 
   NS_FORWARD_NSIDOMEVENTTARGET(nsXHREventTarget::)
 
 #ifdef DEBUG
   void StaticAssertions();

--- a/js/xpconnect/src/dictionary_helper_gen.conf
+++ b/js/xpconnect/src/dictionary_helper_gen.conf
@@ -7,17 +7,16 @@ dictionaries = [
      [ 'EventInit', 'nsIDOMEvent.idl' ],
      [ 'UIEventInit', 'nsIDOMUIEvent.idl' ],
      [ 'MouseEventInit', 'nsIDOMMouseEvent.idl' ],
      [ 'WheelEventInit', 'nsIDOMWheelEvent.idl' ],
      [ 'IDBObjectStoreParameters', 'nsIIDBDatabase.idl' ],
      [ 'IDBIndexParameters', 'nsIIDBObjectStore.idl' ],
      [ 'GeoPositionOptions', 'nsIDOMGeoGeolocation.idl' ],
      [ 'DOMFileMetadataParameters', 'nsIDOMLockedFile.idl' ],
-     [ 'XMLHttpRequestParameters', 'nsIXMLHttpRequest.idl' ],
      [ 'DeviceStorageEnumerationParameters', 'nsIDOMDeviceStorage.idl' ],
      [ 'CameraSize', 'nsIDOMCameraManager.idl' ],
      [ 'CameraRegion', 'nsIDOMCameraManager.idl' ],
      [ 'CameraPosition', 'nsIDOMCameraManager.idl' ],
      [ 'CameraSelector', 'nsIDOMCameraManager.idl' ],
      [ 'CameraPictureOptions', 'nsIDOMCameraManager.idl' ],
      [ 'CameraRecordingOptions', 'nsIDOMCameraManager.idl' ],
      [ 'ArchiveReaderOptions', 'nsIDOMArchiveReader.idl' ],