From fb03af0c02a96cece93f43207ae2232a7e36a266 Mon Sep 17 00:00:00 2001
From: Kris Maglione <maglione.k@gmail.com>
Date: Sat, 19 Sep 2020 16:39:58 +0000
Subject: [PATCH] Bug 1665862: Don't use AutoSafeJSContext in
 XMLHttpRequestWorker. r=nika

It crashes if it fails to create the unprivileged junk scope, which is not
great when it's being used by a fallible function.

Differential Revision: https://phabricator.services.mozilla.com/D90753
---
 dom/xhr/XMLHttpRequestWorker.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/dom/xhr/XMLHttpRequestWorker.cpp b/dom/xhr/XMLHttpRequestWorker.cpp
index 28a0917784bfa..d5c2caae2f59d 100644
--- a/dom/xhr/XMLHttpRequestWorker.cpp
+++ b/dom/xhr/XMLHttpRequestWorker.cpp
@@ -898,7 +898,12 @@ Proxy::HandleEvent(Event* aEvent) {
   }
 
   {
-    AutoSafeJSContext cx;
+    AutoJSAPI jsapi;
+    JSObject* junkScope = xpc::UnprivilegedJunkScope(fallible);
+    if (!junkScope || !jsapi.Init(junkScope)) {
+      return NS_ERROR_FAILURE;
+    }
+    JSContext* cx = jsapi.cx();
 
     JS::Rooted<JS::Value> value(cx);
     if (!GetOrCreateDOMReflectorNoWrap(cx, mXHR, &value)) {