Switch to downloaded SDK executable, drop executables in testing/bin.

tools/test.py

 #!/usr/bin/env python
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import os
 import string
 import subprocess
 import sys
 
 import utils
 
 
 def Main():
   args = sys.argv[1:]
   tools_dir = os.path.dirname(os.path.realpath(__file__))
   dart_script_name = 'test.dart'
   dart_test_script = string.join([tools_dir, dart_script_name], os.sep)
-  command = [utils.DartBinary(), '--checked', dart_test_script] + args
+  command = [utils.CheckedInSdkExecutable(),
+             '--checked', dart_test_script] + args
   exit_code = subprocess.call(command)
   utils.DiagnoseExitCode(exit_code, command)
   return exit_code
 
 
 if __name__ == '__main__':
   sys.exit(Main())