Update chromium_mac recipe for re-imaged testers.

scripts/slave/recipe_modules/chromium/client_skia.py

 # 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.
 
 from . import chromium_linux
 from . import chromium_mac
 from . import chromium_win
 from common.skia import builder_name_schema
 import copy
 
 # The Skia config just clones some regular Chromium builders, except that they
 # use an up-to-date Skia.
 
 # This list specifies which Chromium builders to "copy".
 _builders = [
 #  SPEC Module     Test Spec File         Builder Names
   (chromium_linux, 'chromium.linux.json', ['Linux Builder', 'Linux Tests']),
   (chromium_win,   'chromium.win.json',   ['Win Builder', 'Win7 Tests (1)']),
-  (chromium_mac,   'chromium.mac.json',   ['Mac Builder', 'Mac10.7 Tests (1)']),
+  (chromium_mac,   'chromium.mac.json',   ['Mac Builder', 'Mac10.9 Tests']),
 ]
 
 SPEC = {
   'settings': {
     'build_gs_bucket': 'chromium-skia-gm',
   },
   'builders': {},
 }
 
 for spec_module, test_spec_file, builders_list in _builders:
   for builder in builders_list:
     for builder_name in (builder, builder_name_schema.TrybotName(builder)):
       builder_cfg = copy.deepcopy(spec_module.SPEC['builders'][builder])
       builder_cfg['recipe_config'] = 'chromium_skia'
       builder_cfg['testing']['test_spec_file'] = test_spec_file
       SPEC['builders'][builder_name] = builder_cfg