Add a resynthesis test to verify summarization of generic closures.

pkg/analyzer/test/src/summary/resynthesize_common.dart

Index: pkg/analyzer/test/src/summary/resynthesize_common.dart
diff --git a/pkg/analyzer/test/src/summary/resynthesize_common.dart b/pkg/analyzer/test/src/summary/resynthesize_common.dart
index 213577ac7d858e1a802b4d16a7ec8fcb2724da8a..4f2cd4007f7d85e1ca3e57a43af1088b6ab19812 100644
--- a/pkg/analyzer/test/src/summary/resynthesize_common.dart
+++ b/pkg/analyzer/test/src/summary/resynthesize_common.dart
@@ -1677,6 +1677,10 @@ f() {
 ''');
   }
 
+  test_closure_generic() {
+    checkLibrary('final f = <U, V>(U x, V y) => y;');
+  }
+
   test_closure_in_variable_declaration_in_part() {
     addSource('/a.dart', 'part of lib; final f = (int i) => i.toDouble();');
     checkLibrary('''