Fix #14144 confusing error message misusing a callable object

runtime/lib/errors_patch.dart

Index: runtime/lib/errors_patch.dart
diff --git a/runtime/lib/errors_patch.dart b/runtime/lib/errors_patch.dart
index cf42b572f7c9a7904b0c590174835b36af7ade8b..76bbd7a4e167a63882f35b75cb1c0cc1e22e7073 100644
--- a/runtime/lib/errors_patch.dart
+++ b/runtime/lib/errors_patch.dart
@@ -312,7 +312,8 @@ class NoSuchMethodError {
                   .writeln("The $type_str '$memberName' was called on null.");
             }
           } else {
-            if (_receiver is Function) {
+            if (_receiver.runtimeType == Function ||

[rmacnak, 2017/03/31 16:36:39]

`_receiver.runtimeType == Function` doesn't match anything because Function is
abstract.


class C {
  call() => 42;
}

main() {
  var c = new C();
  print(c.runtimeType == Function);  // false
  print(c is Function);  // true
}

+                _receiver.runtimeType == _Closure) {
               msg_buf.writeln("Closure call with mismatched arguments: "
                   "function '$memberName'");
             } else if (_receiver is _Type && memberName == "call") {