Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/XmlResolverAsync.cs

@@ -0,0 +1,15 @@
+
+using System.Threading.Tasks;
+
+namespace System.Xml {
+
+    public abstract partial class XmlResolver {
+
+        public virtual Task<Object> GetEntityAsync(Uri absoluteUri,
+                                             string role,
+                                             Type ofObjectToReturn) {
+
+            throw new NotImplementedException();
+        }
+    }
+}