From 02075ab97a1c3f2e0ab54d4866442e59fc81d1ac Mon Sep 17 00:00:00 2001
From: Raymond Hill <rhill@raymondhill.net>
Date: Tue, 19 Nov 2019 16:48:53 -0500
Subject: [PATCH] Test for existence of browser.dns

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/780

browser.dns is not available before Firefox 60,
test for presence.
---
 platform/firefox/vapi-webrequest.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/platform/firefox/vapi-webrequest.js b/platform/firefox/vapi-webrequest.js
index e2fcd9201..efbbce280 100644
--- a/platform/firefox/vapi-webrequest.js
+++ b/platform/firefox/vapi-webrequest.js
@@ -167,7 +167,8 @@
             if (
                 typeof list !== 'string' ||
                 list.length === 0 ||
-                list === 'unset'
+                list === 'unset' ||
+                browser.dns instanceof Object === false
             ) {
                 return null;
             }