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

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

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
index 67ca8bce188b6127c091266b79da0dc5c264aa6c..c66ce73dd14db7f7eb2e9faaa0e438738553413a 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
@@ -253,11 +253,10 @@ class Manager(object):
         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)