Deploy more slaves into Mac optional0_slaves pool.

masters/master.tryserver.chromium.mac/slaves.cfg

 # -*- python -*-
 # ex: set syntax=python:
 # Copyright 2014 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.
 
 # See master.experimental/slaves.cfg for documentation.
 
 def mac():
   cq_slaves = (
       ['vm%d-m4' % i for i in ([213, 256, 257, 258, 902, 903, 1000] +
                                range(277, 300) + range(552, 555) +
                                range(682, 711) + range(860, 870) +
                                range(969, 987))])
   cq_builders = [
       'mac_chromium_compile_dbg_ng',
       'mac_chromium_rel_ng',
   ]
 
-  optional0_slaves = ['vm%d-m4' % i for i in [713, 645, 646, 647, 648]]
+  optional0_slaves = ['vm%d-m4' % i for i in ([713, 645, 646, 647, 648] +
+                                              range(783, 788))]
   optional0_builders = [
       'mac_chromium_dbg_ng',
       'mac_chromium_gyp_dbg',
       'mac_chromium_gyp_rel',
       'mac_chromium_gn_upload',
       'mac_upload_clang',
       'mac_optional_gpu_tests_rel',
   ]
 
   optional1_slaves = ['vm723-m4']
@@ skipping 185 matching lines @@
       'pool': 'ios_cq_rel',
     } for slave in cq_slaves_rel]
 
   # TODO(lliabraa): Add test_slaves once we're actually running iOS tests on
   # the bots.
 
   return compile_slaves_dbg + compile_slaves_rel
 
 
 slaves = mac() + ios()