Bug 1696593: Ensure that the DNS service is initted (on main) before trying to...

Bug 1696593: Ensure that the DNS service is initted (on main) before trying to init NrIceCtx. r=mjf,kershaw,necko-reviewers, a=jcristau

Also add some NS_WARN_IF that helped find the bug.

Differential Revision: https://phabricator.services.mozilla.com/D107508

dom/media/webrtc/jsapi/MediaTransportHandler.cpp

@@ -41,6 +41,7 @@
 #include "mozilla/PublicSSL.h"  // For psm::InitializeCipherSuite
 
 #include "nsISocketTransportService.h"
+#include "nsDNSService2.h"
 #include "nsNetUtil.h"  // NS_CheckPortSafety
 
 #include <string>
@@ -528,6 +529,10 @@ nsresult MediaTransportHandlerSTS::CreateIceCtx(
 
         static bool globalInitDone = false;
         if (!globalInitDone) {
+          // Ensure the DNS service is initted for the first time on main
+          DebugOnly<RefPtr<nsIDNSService>> dnsService =
+              RefPtr<nsIDNSService>(nsDNSService::GetXPCOMSingleton());
+          MOZ_ASSERT(dnsService.value);
           mStsThread->Dispatch(
               WrapRunnableNM(&NrIceCtx::InitializeGlobals, GetGlobalConfig()),
               NS_DISPATCH_NORMAL);

dom/media/webrtc/jsapi/moz.build

@@ -12,6 +12,7 @@ LOCAL_INCLUDES += [
     "/dom/media/webrtc",
     "/ipc/chromium/src",
     "/media/webrtc",
+    "/netwerk/dns",  # For nsDNSService2.h
     "/third_party/libsrtp/src/include",
     "/third_party/libwebrtc",
     "/third_party/libwebrtc/webrtc",

dom/media/webrtc/transport/nriceresolver.cpp

@@ -92,7 +92,7 @@ nsresult NrIceResolver::Init() {
   sts_thread_ = do_GetService(NS_SOCKETTRANSPORTSERVICE_CONTRACTID, &rv);
   MOZ_ASSERT(NS_SUCCEEDED(rv));
   dns_ = do_GetService(NS_DNSSERVICE_CONTRACTID, &rv);
-  if (NS_FAILED(rv)) {
+  if (NS_WARN_IF(NS_FAILED(rv))) {
     MOZ_MTLOG(ML_ERROR, "Could not acquire DNS service");
   }
   return rv;

netwerk/dns/ChildDNSService.cpp

@@ -40,7 +40,7 @@ already_AddRefed<ChildDNSService> ChildDNSService::GetSingleton() {
                 XRE_IsContentProcess() || XRE_IsSocketProcess());
 
   if (!gChildDNSService) {
-    if (!NS_IsMainThread()) {
+    if (NS_WARN_IF(!NS_IsMainThread())) {
       return nullptr;
     }
     gChildDNSService = new ChildDNSService();