[test] Correctly merge expected test outcomes.

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 16 matching lines @@
 
 
 from . import output
 
 class TestCase(object):
   def __init__(self, suite, path, flags=None, dependency=None):
     self.suite = suite        # TestSuite object
     self.path = path          # string, e.g. 'div-mod', 'test-api/foo'
     self.flags = flags or []  # list of strings, flags specific to this test
     self.dependency = dependency  # |path| for testcase that must be run first
-    self.outcomes = None
+    self.outcomes = set([])
     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
 
@@ skipping 28 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)