Small fixes to top level type inference.

pkg/front_end/testcases/inference_new/downwards_inference_inside_top_level_2.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*@testedFeatures=inference*/
 library test;
 
-List<T> f<T>(T g()) => <T>[g()];
-var /*@topType=dynamic*/ v = (f) /*@typeArgs=int*/ (/*@returnType=int*/ () {
-  return 1;
-});
+class A<T> {
+  A(T x);
+}
 
-main() {
-  v;
-}
+var /*@topType=List<A<int>>*/ t2 = /*@typeArgs=A<int>*/ [
+  new
+      /*error:TOP_LEVEL_TYPE_ARGUMENTS*/ /*@typeArgs=int*/ A(2)
+];
+
+main() {}