Added support for logging the output of failed flaky tests.

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index c270a10eec2e6ce708dc3ebcb648388b49072c72..06845fafb6dd5242b64081bc06ea5a34a7aca6d8 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -167,6 +167,17 @@ class TestCase {
   bool get usesWebDriver => TestUtils.usesWebDriver(configuration['runtime']);
 
   void completed() { completedHandler(this); }
+
+  bool get isFlaky {
+      if (expectedOutcomes.contains(SKIP)) {
+        return false;
+      }
+
+      var flags = new Set.from(expectedOutcomes);
+      flags..remove(TIMEOUT)
+           ..remove(SLOW);
+      return flags.contains(PASS) && flags.length > 1;
+  }
 }