Replace linux_chromium_headless_dbg with linux_chromium_headless_rel

masters/master.tryserver.chromium.linux/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 linux():
   chromeos_boards = ('x86-generic', 'amd64-generic', 'daisy')
@@ skipping 158 matching lines @@
       'master': 'TryServerChromiumLinux',
       'os': 'linux',
       'version': 'precise',
       'bits': '64',
       'builder': ['linux_layout_tests_slimming_paint_v2'],
       'hostname': 'slave775-c4',
       'pool': 'linux_layout_tests_slimming_paint_v2',
     }
   ])
 
-  # Slaves for linux_chromium_headless_dbg.
+  # Slaves for linux_chromium_headless_rel.
   headless_slaves = [426, 497, 776, 864, 865, 872] + range(1069, 1098)
   for slave in headless_slaves:
     result.append({
       'master': 'TryServerChromiumLinux',
       'os': 'linux',
       'version': 'trusty',
       'bits': 64,
-      'builder': ['linux_chromium_headless_dbg'],
+      'builder': ['linux_chromium_headless_rel'],
       'hostname': 'slave%d-c4' % slave,
-      'pool': 'linux_chromium_headless_dbg',
+      'pool': 'linux_chromium_headless_rel',
     })
 
   return result
 
 
 slaves = linux()