Add flutter_engine runtime to the test script so we can run standard dart tests from the test suite…

tools/testing/dart/runtime_configuration.dart

Index: tools/testing/dart/runtime_configuration.dart
diff --git a/tools/testing/dart/runtime_configuration.dart b/tools/testing/dart/runtime_configuration.dart
index d3747eac06b1479d34cd6ec5755b591e7f39ecac..87fd0f5d9708ca129e9e505ea8117b3b332a4c55 100644
--- a/tools/testing/dart/runtime_configuration.dart
+++ b/tools/testing/dart/runtime_configuration.dart
@@ -58,6 +58,9 @@ class RuntimeConfiguration {
       case 'vm':
         return new StandaloneDartRuntimeConfiguration();
 
+      case 'flutter':
+        return new StandaloneFlutterEngineConfiguration();
+
       case 'dart_precompiled':
         if (configuration['system'] == 'android') {
           return new DartPrecompiledAdbRuntimeConfiguration(useBlobs: useBlobs);
@@ -240,6 +243,29 @@ class StandaloneDartRuntimeConfiguration extends DartVmRuntimeConfiguration {
   }
 }
 
+/// The flutter engine binary, "sky_shell".
+class StandaloneFlutterEngineConfiguration extends DartVmRuntimeConfiguration {
+  List<Command> computeRuntimeCommands(
+      TestSuite suite,
+      CommandBuilder commandBuilder,
+      CommandArtifact artifact,
+      List<String> arguments,
+      Map<String, String> environmentOverrides) {
+    String script = artifact.filename;
+    String type = artifact.mimeType;
+    if (script != null &&
+        type != 'application/dart' &&
+        type != 'application/dart-snapshot') {
+      throw "Flutter Engine cannot run files of type '$type'.";
+    }
+    String executable = suite.flutterEngineBinaryFileName;
+    var args = <String>['--non-interactive']..addAll(arguments);
+    return <Command>[
+      commandBuilder.getVmCommand(executable, args, environmentOverrides)
+    ];
+  }
+}
+
 class DartPrecompiledRuntimeConfiguration extends DartVmRuntimeConfiguration {
   final bool useBlobs;
   DartPrecompiledRuntimeConfiguration({bool useBlobs}) : useBlobs = useBlobs;