Limit the layout_test batch size for *SAN builds.

Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
 # Copyright (C) 2011 Apple Inc. 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.
@@ skipping 282 matching lines @@
     for group_name, group_options in option_group_definitions:
         option_group = optparse.OptionGroup(option_parser, group_name)
         option_group.add_options(group_options)
         option_parser.add_option_group(option_group)
 
     return option_parser.parse_args(args)
 
 
 def _set_up_derived_options(port, options, args):
     """Sets the options values that depend on other options values."""
+    if options.batch_size is None:
+        options.batch_size = port.default_batch_size()
+
     if not options.child_processes:
         options.child_processes = os.environ.get("WEBKIT_TEST_CHILD_PROCESSES",
                                                  str(port.default_child_processes()))
     if not options.max_locked_shards:
         options.max_locked_shards = int(os.environ.get("WEBKIT_TEST_MAX_LOCKED_SHARDS",
                                                        str(port.default_max_locked_shards())))
 
     if not options.configuration:
         options.configuration = port.default_configuration()
 
@@ skipping 63 matching lines @@
         printer.print_config(port.results_directory())
 
         run_details = manager.run(args)
         _log.debug("Testing completed, Exit status: %d" % run_details.exit_code)
         return run_details
     finally:
         printer.cleanup()
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv[1:], sys.stdout, sys.stderr))