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 20 matching lines @@
 class TestCase(object):
   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
+    self.run = 1  # The nth time this test is executed.
 
   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.
     """
     assert self.id is not None
     return [self.suitename(), self.path, self.flags,
             self.dependency, list(self.outcomes or []), self.id]
 
   @staticmethod
   def UnpackTask(task):
     """Creates a new TestCase object based on packed task data."""
     # For the order of the fields, refer to PackTask() above.
     test = TestCase(str(task[0]), task[1], task[2], task[3])
     test.outcomes = set(task[4])
     test.id = task[5]
+    test.run = 1
     return test
 
   def SetSuiteObject(self, suites):
     self.suite = suites[self.suite]
 
   def PackResult(self):
     """Serializes the output of the TestCase after it has run."""
     self.suite.StripOutputForTransmit(self)
     return [self.id, self.output.Pack(), self.duration]
 
   def MergeResult(self, result):
     """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)