--- a/dom/promise/Promise.cpp
+++ b/dom/promise/Promise.cpp
@@ -36,16 +36,17 @@
 #include "nsJSPrincipals.h"
 #include "nsJSUtils.h"
 #include "nsPIDOMWindow.h"
 #include "PromiseDebugging.h"
 #include "PromiseNativeHandler.h"
 #include "PromiseWorkerProxy.h"
 #include "WrapperFactory.h"
 #include "xpcpublic.h"
+#include "xpcprivate.h"
 
 namespace mozilla {
 namespace dom {
 
 namespace {
 // Generator used by Promise::GetID.
 Atomic<uintptr_t> gIDGenerator(0);
 }  // namespace
@@ -543,16 +544,42 @@ void Promise::ReportRejectedPromise(JSCo
   RefPtr<nsIRunnable> event = new AsyncErrorReporter(xpcReport);
   if (win) {
     win->Dispatch(mozilla::TaskCategory::Other, event.forget());
   } else {
     NS_DispatchToMainThread(event);
   }
 }
 
+void Promise::MaybeResolveWithClone(JSContext* aCx,
+                                    JS::Handle<JS::Value> aValue) {
+  JS::Rooted<JSObject*> sourceScope(aCx, JS::CurrentGlobalOrNull(aCx));
+  AutoEntryScript aes(GetParentObject(), "Promise resolution");
+  JSContext* cx = aes.cx();
+  JS::Rooted<JS::Value> value(cx, aValue);
+
+  xpc::StackScopedCloneOptions options;
+  options.wrapReflectors = true;
+  StackScopedClone(cx, options, sourceScope, &value);
+  MaybeResolve(aCx, value);
+}
+
+void Promise::MaybeRejectWithClone(JSContext* aCx,
+                                   JS::Handle<JS::Value> aValue) {
+  JS::Rooted<JSObject*> sourceScope(aCx, JS::CurrentGlobalOrNull(aCx));
+  AutoEntryScript aes(GetParentObject(), "Promise rejection");
+  JSContext* cx = aes.cx();
+  JS::Rooted<JS::Value> value(cx, aValue);
+
+  xpc::StackScopedCloneOptions options;
+  options.wrapReflectors = true;
+  StackScopedClone(cx, options, sourceScope, &value);
+  MaybeReject(aCx, value);
+}
+
 JSObject* Promise::GlobalJSObject() const {
   return mGlobal->GetGlobalJSObject();
 }
 
 JS::Compartment* Promise::Compartment() const {
   return js::GetObjectCompartment(GlobalJSObject());
 }
 

--- a/dom/promise/Promise.h
+++ b/dom/promise/Promise.h
@@ -98,16 +98,19 @@ class Promise : public nsISupports, publ
     MOZ_ASSERT(aArg.Failed());
     MaybeSomething(aArg, &Promise::MaybeReject);
   }
 
   void MaybeReject(const RefPtr<MediaStreamError>& aArg);
 
   void MaybeRejectWithUndefined();
 
+  void MaybeResolveWithClone(JSContext* aCx, JS::Handle<JS::Value> aValue);
+  void MaybeRejectWithClone(JSContext* aCx, JS::Handle<JS::Value> aValue);
+
   // DO NOT USE MaybeRejectBrokenly with in new code.  Promises should be
   // rejected with Error instances.
   // Note: MaybeRejectBrokenly is a template so we can use it with DOMException
   // without instantiating the DOMException specialization of MaybeSomething in
   // every translation unit that includes this header, because that would
   // require use to include DOMException.h either here or in all those
   // translation units.
   template <typename T>

--- a/dom/promise/moz.build
+++ b/dom/promise/moz.build
@@ -18,16 +18,17 @@ EXPORTS.mozilla.dom += [
 UNIFIED_SOURCES += [
     'Promise.cpp',
     'PromiseDebugging.cpp',
 ]
 
 LOCAL_INCLUDES += [
     '../base',
     '../ipc',
+    '/js/xpconnect/src',
 ]
 
 include('/ipc/chromium/chromium-config.mozbuild')
 
 FINAL_LIBRARY = 'xul'
 
 MOCHITEST_MANIFESTS += ['tests/mochitest.ini']