Bug 1873461 - Add pref for resolving HTTPS records using native resol…

…ver on win 10 r=necko-reviewers,jesup

Differential Revision: https://phabricator.services.mozilla.com/D198020

modules/libpref/init/StaticPrefList.yaml

@@ -11921,6 +11921,14 @@
   value: false
   mirror: always
 
+# DnsQuery_A is broken for HTTPS queries on Windows 10.
+# Once it gets fixed, we can flip this pref to enable it.
+# Changes might not take effect until restart.
+- name: network.dns.native_https_query_win10
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 # When resolving a native HTTPS query with native APIs
 # the Android implementation has a max timeout
 - name: network.dns.native_https_timeout_android

netwerk/dns/nsHostResolver.cpp

@@ -235,7 +235,8 @@ nsresult nsHostResolver::Init() MOZ_NO_THREAD_SAFETY_ANALYSIS {
   // For some reason, the DNSQuery_A API doesn't work on Windows 10.
   // It returns a success code, but no records. We only allow
   // native HTTPS records on Win 11 for now.
-  sNativeHTTPSSupported = mozilla::IsWin11OrLater();
+  sNativeHTTPSSupported = StaticPrefs::network_dns_native_https_query_win10() ||
+                          mozilla::IsWin11OrLater();
 #elif defined(MOZ_WIDGET_ANDROID)
   // android_res_nquery only got added in API level 29
   sNativeHTTPSSupported = jni::GetAPIVersion() >= 29;