restarting adb server before each testing start will cause conflict for multiple emulators

build/android/run_tests.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012 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.
 
 """Runs all the native unit tests.
 
 1. Copy over test binary to /data/local on device.
 2. Resources: chrome/unit_tests requires resources (chrome.pak and en-US.pak)
@@ skipping 408 matching lines @@
                            'of failures.')
   option_parser.add_option('--exe', action='store_true',
                            help='If set, use the exe test runner instead of '
                            'the APK.')
   options, args = option_parser.parse_args(argv)
   if len(args) > 1:
     print 'Unknown argument:', args[1:]
     option_parser.print_usage()
     sys.exit(1)
   run_tests_helper.SetLogLevel(options.verbose_count)
+  emulator.DeleteAllTempAVDs()
   failed_tests_count = Dispatch(options)
 
   # Failures of individual test suites are communicated by printing a
   # STEP_FAILURE message.
   # Returning a success exit status also prevents the buildbot from incorrectly
   # marking the last suite as failed if there were failures in other suites in
   # the batch (this happens because the exit status is a sum of all failures
   # from all suites, but the buildbot associates the exit status only with the
   # most recent step).
   if options.exit_code:
     return failed_tests_count
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))