Make copy of flags before passing it to TestCompiler

utils/compiler/buildbot.py

 #!/usr/bin/python
 
 # Copyright (c) 2011 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.
 
 """Dart2js buildbot steps
 
 Runs tests for the  dart2js compiler.
 """
@@ skipping 373 matching lines @@
   test_flags = []
   if build_info.shard_index:
     test_flags = ['--shards=%s' % build_info.total_shards,
                   '--shard=%s' % build_info.shard_index]
 
   if build_info.checked: test_flags += ['--checked']
 
   if build_info.host_checked: test_flags += ['--host-checked']
 
   status = TestCompiler(build_info.runtime, build_info.mode,
-                        build_info.system, test_flags,
+                        build_info.system, list(test_flags),
                         build_info.is_buildbot, build_info.test_set)
 
   # See comment in GetHasHardCodedCheckedMode, this is a hack.
   if (status == 0 and GetHasHardCodedCheckedMode(build_info)):
     status = TestCompiler(build_info.runtime, build_info.mode,
                           build_info.system,
                           test_flags  + ['--checked'],
                           build_info.is_buildbot,
                           build_info.test_set)
 
   if build_info.runtime != 'd8': CleanUpTemporaryFiles(build_info.system,
                                                        build_info.runtime)
   if status != 0: print '@@@STEP_FAILURE@@@'
   return status
 
 if __name__ == '__main__':
   sys.exit(main())