Fix annotation of generic method invocations in Fasta inference tests.

pkg/front_end/testcases/inference/future_union_downwards.dart

Index: pkg/front_end/testcases/inference/future_union_downwards.dart
diff --git a/pkg/front_end/testcases/inference/future_union_downwards.dart b/pkg/front_end/testcases/inference/future_union_downwards.dart
index fd3c9bed94646babb5180574e4e2bef3ed5428e0..5914cef14b283b88f4c9292eaaeef9af549deb45 100644
--- a/pkg/front_end/testcases/inference/future_union_downwards.dart
+++ b/pkg/front_end/testcases/inference/future_union_downwards.dart
@@ -16,11 +16,12 @@ class MyFuture<T> implements Future<T> {
 
 MyFuture f;
 // Instantiates Future<int>
-Future<int> t1 = f.then(/*@returnType=Future<int>*/ (/*@type=dynamic*/ _) =>
-    new /*@typeArgs=int*/ Future.value('hi'));
+Future<int> t1 = f. /*@typeArgs=int*/ then(
+    /*@returnType=Future<int>*/ (/*@type=dynamic*/ _) =>
+        new /*@typeArgs=int*/ Future.value('hi'));
 
 // Instantiates List<int>
-Future<List<int>> t2 = f.then(
+Future<List<int>> t2 = f. /*@typeArgs=List<int>*/ then(
     /*@returnType=List<int>*/ (/*@type=dynamic*/ _) => /*@typeArgs=int*/ [3]);
 Future<List<int>> g2() async {
   return /*@typeArgs=int*/ [3];