cleanup to tools/testing/dart

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 1358b01684559e16dccce9383c7da19e8c7c05a2..2743723621cd1dce5099e05f15dc39c85b8b169d 100644
--- a/tools/testing/dart/runtime_configuration.dart
+++ b/tools/testing/dart/runtime_configuration.dart
@@ -4,18 +4,28 @@
 
 library runtime_configuration;
 
-import 'compiler_configuration.dart' show
-    CommandArtifact;
-
 // TODO(ahe): Remove this import, we can precompute all the values required
 // from TestSuite once the refactoring is complete.
 import 'test_suite.dart' show
     TestSuite;
 
-import 'test_runner.dart' show
+import 'lib/command.dart' show
     Command,
     CommandBuilder;
 
+/// Grouping of a command with its expected result.
+class CommandArtifact {
+  final List<Command> commands;
+
+  /// Expected result of running [command].
+  final String filename;
+
+  /// MIME type of [filename].
+  final String mimeType;
+
+  CommandArtifact(this.commands, this.filename, this.mimeType);
+}
+
 // TODO(ahe): I expect this class will become abstract very soon.
 class RuntimeConfiguration {
   // TODO(ahe): Remove this constructor and move the switch to