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..374e242e14662235124b256c6552201c4cbbb65e 100644
--- a/tools/testrunner/objects/testcase.py
+++ b/tools/testrunner/objects/testcase.py
@@ -38,6 +38,7 @@ class TestCase(object):
     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)
@@ -51,7 +52,7 @@ class TestCase(object):
     """
     assert self.id is not None
     return [self.suitename(), self.path, self.flags,
-            self.dependency, list(self.outcomes or []), self.id]
+            self.dependency, list(self.outcomes or []), self.id, self.run]

[Jakob Kummerow, 2014/07/02 07:27:26]

IIUC, |run| is always 1 when a test is packed for network transmission. So we
could skip the value here...

[Michael Achenbach, 2014/07/02 08:06:33]

Done.

 
   @staticmethod
   def UnpackTask(task):
@@ -60,6 +61,7 @@ class TestCase(object):
     test = TestCase(str(task[0]), task[1], task[2], task[3])
     test.outcomes = set(task[4])
     test.id = task[5]
+    test.run = task[6]

[Jakob Kummerow, 2014/07/02 07:27:26]

...and  simply fill in 1 here (or not set it at all, as the constructor defaults
to 1 anyway). Sending bytes over the wire is fairly expensive, compared to
almost anything else the test runner does.

[Michael Achenbach, 2014/07/02 08:06:33]

Done.

     return test
 
   def SetSuiteObject(self, suites):