Reuse -cdartk for vm testing with Dart Frontend parser.

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index e6a8e3ab02ed372a7379393878b694e0ef7e9cac..13f782627774e9518e08ba28510194603d8f601d 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -2040,6 +2040,13 @@ class TestUtils {
     if (compiler == "dart2js" && configuration["dart2js_with_kernel"]) {
       args.add("--use-kernel");
     }
+    if (compiler == "none" &&
+        configuration["kernel_snapshot_to_use_in_vm"] != '') {
+      // Kernel snapshot argument should be first in the list.
+      args.insert(0,
+          "--run_vm_test_with_kernel_snapshot=${configuration['kernel_snapshot_to_use_in_vm']}");
+      args.add("--use_dart_frontend");

[siva, 2017/05/15 04:42:56]

Why not use the same scheme as used with the compiler=dartk option in the
regular testing it picks up the kernel snapshot from
{buildDir}/gen/kernel-service.dart.snapshot

[aam, 2017/05/16 00:18:02]

If we are to support vm testing with or without kernel parser we still would
have to introduce an option. Or were you thinking something along the lines of
introducing new compiler(something like none_dfe as alternative to none)?
If we are to introduce an option, I thought we might as well make it a
string(snapshot name), rather than a boolean option(dfe)?

[siva, 2017/05/17 18:36:46]

I was thinking if we changed test_configuration.dart to include compiler ==
dartk we would be able to reuse all the stuff that is setup for dartk in the
regular tests

            (conf['compiler'] == 'none' || conf['compiler'] == 'dartk') &&
            conf['runtime'] == 'vm' &&
            key == 'vm') {
          // vm tests contain both cc tests (added here) and dart tests (added
          // in [TEST_SUITE_DIRECTORIES]).
          testSuites.add(new VMTestSuite(conf));

Then we should be able to run the test as 

tools/test.py -cdartk vm

+    }
     return args;
   }