Improve reproducibility of test runs.

tools/testrunner/objects/context.py

Index: tools/testrunner/objects/context.py
diff --git a/tools/testrunner/objects/context.py b/tools/testrunner/objects/context.py
index 1f525b76b3114793b3548f2c740e7427805be0fc..68c19892410bf63643c17fe70c358d47cb69e327 100644
--- a/tools/testrunner/objects/context.py
+++ b/tools/testrunner/objects/context.py
@@ -28,7 +28,7 @@
 
 class Context():
   def __init__(self, arch, mode, shell_dir, mode_flags, verbose, timeout,
-               isolates, command_prefix, extra_flags, noi18n):
+               isolates, command_prefix, extra_flags, noi18n, random_seed):
     self.arch = arch
     self.mode = mode
     self.shell_dir = shell_dir
@@ -39,13 +39,16 @@ class Context():
     self.command_prefix = command_prefix
     self.extra_flags = extra_flags
     self.noi18n = noi18n
+    self.random_seed = random_seed
 
   def Pack(self):
     return [self.arch, self.mode, self.mode_flags, self.timeout, self.isolates,
-            self.command_prefix, self.extra_flags, self.noi18n]
+            self.command_prefix, self.extra_flags, self.noi18n,
+            self.random_seed]
 
   @staticmethod
   def Unpack(packed):
     # For the order of the fields, refer to Pack() above.
     return Context(packed[0], packed[1], None, packed[2], False,
-                   packed[3], packed[4], packed[5], packed[6], packed[7])
+                   packed[3], packed[4], packed[5], packed[6], packed[7],
+                   packed[8])