Add Mac10.12 continuous builder and try bot config (src repo).

testing/buildbot/manage.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Toolbox to manage all the json files in this directory.
 
 It can reformat them in their canonical format or ensures they are well
 formatted.
 """
@@ skipping 42 matching lines @@
   # Android bots need custom dimension_sets entries for swarming, and capacity
   # is not there yet -- so don't let manage.py add swarming automatically there.
   'Android User Builder Tests',
   'Android GN',
   'Android Tests',
   'Android Tests (dbg)',
 
   # http://crbug.com/441429
   'Linux Trusty (32)', 'Linux Trusty (dbg)(32)',
 
-  # swarming may not work on Mac10.10 and 10.11, need to
-  # re-investigate and confirm
+  # Swarming may not work on Mac10.10,11,12; need to
+  # re-investigate and confirm.
   'WebKit Mac10.10',
   'WebKit Mac10.11',
+  'WebKit Mac10.12',
   'WebKit Mac10.11 (dbg)',
   'WebKit Mac10.11 (retina)',
   'Chromium Mac10.10 Tests',
   'Chromium Mac10.11 Tests',
   'Mac GN',
   'Mac GN (dbg)',
 
   # The memory.fyi waterfall is in the process of being converted to recipes,
   # and swarming doesn't work yet.
   'Chromium Mac (valgrind)(1)',
@@ skipping 410 matching lines @@
     elif args.mode == 'remaining':
       print_remaining(args.test_name, tests_location)
     return result
   except Error as e:
     sys.stderr.write('%s\n' % e)
     return 1
 
 
 if __name__ == "__main__":
   sys.exit(main())