Let test runner rerun failures to test for flakes.

tools/testrunner/objects/testcase.py

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 21 matching lines @@
   def __init__(self, suite, path, flags=[], dependency=None):
     self.suite = suite  # TestSuite object
     self.path = path    # string, e.g. 'div-mod', 'test-api/foo'
     self.flags = flags  # list of strings, flags specific to this test case
     self.dependency = dependency  # |path| for testcase that must be run first
     self.outcomes = None
     self.output = None
     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
     return copy
 
   def PackTask(self):
     """
     Extracts those parts of this object that are required to run the test
     and returns them as a JSON serializable object.
     """
@@ skipping 22 matching lines @@
     """Applies the contents of a Result to this object."""
     assert result[0] == self.id
     self.output = output.Output.Unpack(result[1])
     self.duration = result[2]
 
   def suitename(self):
     return self.suite.name
 
   def GetLabel(self):
     return self.suitename() + "/" + self.suite.CommonTestName(self)