[cq] Keep presubmit trybots and cq automatically in sync.

PRESUBMIT.py

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 260 matching lines @@
   results.extend(input_api.canned_checks.CheckChangeHasDescription(
       input_api, output_api))
   if not _SkipTreeCheck(input_api, output_api):
     results.extend(input_api.canned_checks.CheckTreeIsOpen(
         input_api, output_api,
         json_url='http://v8-status.appspot.com/current?format=json'))
   return results
 
 
 def GetPreferredTryMasters(project, change):
-  return {
-    'tryserver.v8': {
-      'v8_linux_rel_ng': set(['defaulttests']),
-      'v8_linux_dbg_ng': set(['defaulttests']),
-      'v8_linux_nodcheck_rel': set(['defaulttests']),
-      'v8_linux_gcc_compile_rel': set(['defaulttests']),
-      'v8_linux64_rel_ng': set(['defaulttests']),
-      'v8_linux64_asan_rel': set(['defaulttests']),
-      'v8_linux64_avx2_rel': set(['defaulttests']),
-      'v8_win_rel_ng': set(['defaulttests']),
-      'v8_win_compile_dbg': set(['defaulttests']),
-      'v8_win_nosnap_shared_compile_rel': set(['defaulttests']),
-      'v8_win64_rel_ng': set(['defaulttests']),
-      'v8_mac_rel': set(['defaulttests']),
-      'v8_linux_arm_rel': set(['defaulttests']),
-      'v8_linux_arm64_rel': set(['defaulttests']),
-      'v8_linux_mipsel_compile_rel': set(['defaulttests']),
-      'v8_linux_mips64el_compile_rel': set(['defaulttests']),
-      'v8_android_arm_compile_rel': set(['defaulttests']),
-      'v8_linux_chromium_gn_rel': set(['defaulttests']),
-    },
-  }
+  import json
+  import os.path
+  import platform
+  import subprocess
+
+  cq_config_path = os.path.join(
+      change.RepositoryRoot(), 'infra', 'config', 'cq.cfg')
+  # commit_queue.py below is a script in depot_tools directory, which has a
+  # 'builders' command to retrieve a list of CQ builders from the CQ config.
+  is_win = platform.system() == 'Windows'
+  masters = json.loads(subprocess.check_output(
+      ['commit_queue', 'builders', cq_config_path], shell=is_win))
+
+  try_config = {}
+  for master in masters:
+    try_config.setdefault(master, {})
+    for builder in masters[master]:
+      # Do not trigger presubmit builders, since they're likely to fail
+      # (e.g. OWNERS checks before finished code review), and we're
+      # running local presubmit anyway.
+      if 'presubmit' not in builder:
+        try_config[master][builder] = ['defaulttests']
+
+  return try_config