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

tools/mb/mb_config.pyl

 # 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.
 
 # This is a .pyl, or "Python Literal", file. You can treat it just like a
 # .json file, with the following exceptions:
 # * all keys must be quoted (use single quotes, please);
 # * comments are allowed, using '#' syntax; and
 # * trailing commas are allowed.
 
@@ skipping 381 matching lines @@
     'chromium.webkit': {
       'Android Builder': 'android_release_bot_minimal_symbols',
       'WebKit Linux Trusty ASAN': 'asan_lsan_release_bot',
       'WebKit Linux Trusty (dbg)': 'debug_bot',
       'WebKit Linux Trusty Leak': 'release_bot',
       'WebKit Linux Trusty MSAN': 'msan_release_bot',
       'WebKit Linux Trusty': 'release_bot',
       'WebKit Mac Builder (dbg)': 'debug_bot',
       'WebKit Mac Builder': 'release_bot',
       'WebKit Mac10.11 (retina)': 'release_bot',
+      'WebKit Mac10.12': 'release_bot',
       'WebKit Mac10.9': 'release_bot',
       'WebKit Win Builder (dbg)': 'debug_bot_x86',
       'WebKit Win Builder': 'release_bot_x86',
       'WebKit Win x64 Builder (dbg)': 'debug_bot',
       'WebKit Win x64 Builder': 'release_bot',
     },
 
     'chromium.webrtc': {
       'Linux Builder': 'release_bot_chrome_with_codecs',
       'Mac Builder': 'chrome_with_codecs_blink_logging_release_trybot',
@@ skipping 69 matching lines @@
       'linux_trusty_blink_compile_rel': 'release_bot_minimal_symbols',
       'linux_trusty_blink_dbg': 'debug_trybot',
       'linux_trusty_blink_rel': 'release_bot_minimal_symbols',
       'mac10.9_blink_compile_dbg': 'debug_trybot',
       'mac10.9_blink_compile_rel': 'release_bot_minimal_symbols',
       'mac10.9_blink_dbg': 'debug_trybot',
       'mac10.9_blink_rel': 'release_bot_minimal_symbols',
       'mac10.10_blink_rel': 'release_bot_minimal_symbols',
       'mac10.11_blink_rel': 'release_bot_minimal_symbols',
       'mac10.11_retina_blink_rel': 'release_bot_minimal_symbols',
+      'mac10.12_blink_rel': 'release_bot_minimal_symbols',
       'win7_blink_compile_dbg': 'debug_trybot_x86',
       'win7_blink_compile_rel': 'release_bot_x86',
       'win7_blink_dbg': 'debug_trybot_x86',
       'win7_blink_rel': 'release_bot_x86',
       'win10_blink_rel': 'release_bot_x86',
     },
 
     'tryserver.chromium.android': {
       'android_archive_rel_ng': 'android_release_trybot',
       'android_arm64_dbg_recipe': 'android_debug_trybot_arm64',
@@ skipping 1436 matching lines @@
 
     'x64': {
       'gn_args': 'target_cpu="x64"',
     },
 
     'x86': {
       'gn_args': 'target_cpu="x86"',
     },
   },
 }