Add --step_name option to test.dart.

dart/tools/testing/dart/test_progress.dart

Index: dart/tools/testing/dart/test_progress.dart
diff --git a/dart/tools/testing/dart/test_progress.dart b/dart/tools/testing/dart/test_progress.dart
index 8066899209c7e1e3cad83f0a429642c4b0ca209c..ef058b10ee23b8462cd4c6d894bfa47f8fce997d 100644
--- a/dart/tools/testing/dart/test_progress.dart
+++ b/dart/tools/testing/dart/test_progress.dart
@@ -14,7 +14,8 @@ class ProgressIndicator {
 
   factory ProgressIndicator.fromName(String name,
                                      Date startTime,
-                                     bool printTiming) {
+                                     bool printTiming,
+                                     String stepName) {
     switch (name) {
       case 'compact':
         return new CompactProgressIndicator(startTime, printTiming);
@@ -29,7 +30,7 @@ class ProgressIndicator {
       case 'status':
         return new StatusProgressIndicator(startTime, printTiming);
       case 'buildbot':
-        return new BuildbotProgressIndicator(startTime, printTiming);
+        return new BuildbotProgressIndicator(startTime, printTiming, stepName);
       default:
         assert(false);
         break;
@@ -340,7 +341,9 @@ class StatusProgressIndicator extends ProgressIndicator {
 
 
 class BuildbotProgressIndicator extends ProgressIndicator {
-  BuildbotProgressIndicator(Date startTime, bool printTiming)
+  final String stepName;
+
+  BuildbotProgressIndicator(Date startTime, bool printTiming, this.stepName)
       : super(startTime, printTiming);
 
   void _printStartProgress(TestCase test) {
@@ -359,15 +362,8 @@ class BuildbotProgressIndicator extends ProgressIndicator {
 
   void _printFailureSummary() {
     if (!_failureSummary.isEmpty()) {
-      // We need to create a unique name for each step, otherwise, the
-      // build bot will show the same failure when several steps
-      // fail. We don't know the name of the current step as it is
-      // printed by the program invoking this.
-      // TODO(ahe): Pass in the step name as an option, and let
-      // test.py take care of printing the steps.
-      var name = 'failures ($_startTime)';
       print('@@@STEP_FAILURE@@@');
-      print('@@@BUILD_STEP $name@@@');
+      print('@@@BUILD_STEP $stepName failures@@@');
     }
     super._printFailureSummary();
   }