Allow seeding the random layout test order and write out seed.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
 #
 # 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
@@ skipping 235 matching lines @@
         tests_to_run = [test for test in test_names if test not in tests_to_skip]
 
         if not tests_to_run:
             return tests_to_run, tests_to_skip
 
         # Create a sorted list of test files so the subset chunk,
         # if used, contains alphabetically consecutive tests.
         if self._options.order == 'natural':
             tests_to_run.sort(key=self._port.test_key)
         elif self._options.order == 'random':
-            random.shuffle(tests_to_run)
-        elif self._options.order == 'random-seeded':
-            rnd = random.Random()
-            rnd.seed(4)  # http://xkcd.com/221/
-            rnd.shuffle(tests_to_run)
+            tests_to_run.sort()
+            rand = random.Random()
+            rand.seed(self._options.seed)

[Dirk Pranke, 2016/09/09 19:50:22]

Nit: this can be 

    rand = random.Random(self._options.seed)

I think.

+            rand.shuffle(tests_to_run)
 
         tests_to_run, tests_in_other_chunks = self._finder.split_into_chunks(tests_to_run)
         self._expectations.add_extra_skipped_tests(tests_in_other_chunks)
         tests_to_skip.update(tests_in_other_chunks)
 
         return tests_to_run, tests_to_skip
 
     def _test_input_for_file(self, test_file):
         return TestInput(test_file,
                          self._options.slow_time_out_ms if self._test_is_slow(test_file) else self._options.time_out_ms,
@@ skipping 282 matching lines @@
 
         stats = {}
         for result in initial_results.results_by_name.values():
             if result.type != test_expectations.SKIP:
                 stats[result.test_name] = {'results': (_worker_number(result.worker_name), result.test_number, result.pid, int(
                     result.test_run_time * 1000), int(result.total_run_time * 1000))}
         stats_trie = {}
         for name, value in stats.iteritems():
             json_results_generator.add_path_to_trie(name, value, stats_trie)
         return stats_trie