Bug 1358043 - Produce only warning when appcache/old cache backend I/O thread can't be created for lack of resources, r=michal

netwerk/cache/nsCacheService.cpp

@@ -1166,7 +1166,7 @@ nsCacheService::Init()
     rv = NS_NewNamedThread("Cache I/O",
                            getter_AddRefs(mCacheIOThread));
     if (NS_FAILED(rv)) {
-        MOZ_CRASH("Can't create cache IO thread");
+        NS_WARNING("Can't create cache IO thread");
     }
 
     rv = nsDeleteDir::Init();