Add better error messages to the webkit_tests step in the android buildbot code.

build/android/buildbot/bb_device_steps.py

 #!/usr/bin/env python
 # Copyright (c) 2013 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.
 
 import collections
 import glob
 import hashlib
 import json
 import multiprocessing
@@ skipping 245 matching lines @@
         ['--additional-expectations=%s' % os.path.join(CHROME_SRC_DIR, *f)])
 
   # TODO(dpranke): Remove this block after
   # https://codereview.chromium.org/12927002/ lands.
   for f in options.factory_properties.get('additional_expectations_files', []):
     cmd_args.extend(
         ['--additional-expectations=%s' % os.path.join(CHROME_SRC_DIR, *f)])
 
   exit_code = RunCmd(['webkit/tools/layout_tests/run_webkit_tests.py'] +
                      cmd_args)
-  if exit_code == 254:  # AKA -1, internal error.
+  if exit_code == 254: # test_run_results.UNEXPECTED_ERROR_EXIT_STATUS
     bb_annotations.PrintMsg('?? (crashed or hung)')
+  elif exit_code == 253: # test_run_results.NO_DEVICES_EXIT_STATUS
+    bb_annotations.PrintMsg('?? (no devices found)')
+  elif exit_code == 252: # test_run_results.NO_TESTS_EXIT_STATUS
+    bb_annotations.PrintMsg('?? (no tests found)')
   else:
     full_results_path = os.path.join('..', 'layout-test-results',
                                      'full_results.json')
     if os.path.exists(full_results_path):
       full_results = json.load(open(full_results_path))
       unexpected_passes, unexpected_failures, unexpected_flakes = (
           _ParseLayoutTestResults(full_results))
       if unexpected_failures:
         _PrintDashboardLink('failed', unexpected_failures,
                             max_tests=25)
@@ skipping 300 matching lines @@
   setattr(options, 'target', options.factory_properties.get('target', 'Debug'))
   if options.coverage_bucket:
     setattr(options, 'coverage_dir',
             os.path.join(CHROME_OUT_DIR, options.target, 'coverage'))
 
   MainTestWrapper(options)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))