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 c95ad9474769c884a7247c645d7d18700adbd2d6..45073820d538baa26aa6628c9c62abde0bef653e 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -472,6 +472,12 @@ class CCTestSuite extends TestSuite {
     var expectations = testExpectations.expectations('$testPrefix$testName');
 
     var args = TestUtils.standardOptions(configuration);
+    var compilerConfiguration = new CompilerConfiguration(configuration);
+    if (compilerConfiguration.useDFE) {
+      args.add('--use-dart-frontend');
+      // '--dfe' has to be the first argument for run_vm_test to pick it up.
+      args.insert(0, '--dfe=$buildDir/gen/kernel-service.dart.snapshot');
+    }
     args.add(testName);
 
     var command = CommandBuilder.instance.getProcessCommand(