Let test runner rerun failures to test for flakes.

tools/testrunner/objects/testcase.py

Index: tools/testrunner/objects/testcase.py
diff --git a/tools/testrunner/objects/testcase.py b/tools/testrunner/objects/testcase.py
index cfc522ea7380c1fef996c4491de1f39352553a16..932588d56f82d471cbfc5411c284edfb65ae702d 100644
--- a/tools/testrunner/objects/testcase.py
+++ b/tools/testrunner/objects/testcase.py
@@ -39,6 +39,12 @@ class TestCase(object):
     self.id = None  # int, used to map result back to TestCase instance
     self.duration = None  # assigned during execution
 
+  def Copy(self):
+    copy = TestCase(self.suite, self.path, self.flags, self.dependency)
+    copy.outcomes = self.outcomes
+    copy.id = self.id
+    return copy
+
   def CopyAddingFlags(self, flags):
     copy = TestCase(self.suite, self.path, self.flags + flags, self.dependency)
     copy.outcomes = self.outcomes