Use package:stack_trace in unittest.

pkg/unittest/lib/compact_vm_config.dart

Index: pkg/unittest/lib/compact_vm_config.dart
diff --git a/pkg/unittest/lib/compact_vm_config.dart b/pkg/unittest/lib/compact_vm_config.dart
index 7c4b0d696907051173f1dbcdeaddff409db1ad26..db42cfc2b3e9ce127186912bf1b0ce52a2535512 100644
--- a/pkg/unittest/lib/compact_vm_config.dart
+++ b/pkg/unittest/lib/compact_vm_config.dart
@@ -11,7 +11,9 @@
 library compact_vm_config;
 
 import 'dart:io';
+
 import 'unittest.dart';
+import 'src/utils.dart';
 import 'vm_config.dart';
 
 const String _GREEN = '\u001b[32m';
@@ -48,19 +50,15 @@ class CompactVMConfiguration extends VMConfiguration {
       _progressLine(_start, _pass, _fail, test.description);
       print('');
       if (test.message != '') {
-        print(_indent(test.message));
+        print(indent(test.message));
       }
 
-      if (test.stackTrace != null && test.stackTrace != '') {
-        print(_indent(test.stackTrace));
+      if (test.stackTrace != null) {
+        print(indent(test.stackTrace.toString()));
       }
     }
   }
 
-  String _indent(String str) {
-    return str.split("\n").map((line) => "  $line").join("\n");
-  }
-
   void onSummary(int passed, int failed, int errors, List<TestCase> results,
       String uncaughtError) {
     var success = false;