[vm/aot] Add kernel AST verification to TFA transformer test

TEST=pkg/vm/test/transformations/type_flow/transformer_test.dart

Change-Id: I491443e84fe94825604708c0ecb8e8e518e35a6f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/401642
Auto-Submit: Alexander Markov <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: alexmarkov

pkg/vm/test/transformations/type_flow/transformer_test.dart

@@ -12,6 +12,7 @@ import 'package:kernel/ast.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/kernel.dart';
 import 'package:kernel/target/targets.dart';
+import 'package:kernel/verifier.dart';
 import 'package:test/test.dart';
 import 'package:vm/modular/target/install.dart' show installAdditionalTargets;
 import 'package:vm/transformations/pragma.dart'
@@ -87,6 +88,9 @@ void runTestCase(
 
   compareResultWithExpectationsFile(source, actual);
 
+  verifyComponent(
+      target, VerificationStage.afterGlobalTransformations, component);
+
   ensureKernelCanBeSerializedToBinary(component);
 }