Move a helper function to find out Dart binary into utils.py

tools/utils.py

 # Copyright (c) 2012, 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.
 
 # This file contains a set of utilities functions used by other Python-based
 # scripts.
 
 import commands
 import os
 import platform
@@ skipping 279 matching lines @@
   if IsCrashExitCode(exit_code):
     sys.stderr.write('Command: %s\nCRASHED with exit code %d (0x%x)\n' % (
         ' '.join(command), exit_code, exit_code & 0xffffffff))
 
 
 def Touch(name):
   with file(name, 'a'):
     os.utime(name, None)
 
 
+def DartBinary():
+  tools_dir = os.path.dirname(os.path.realpath(__file__))
+  dart_binary_prefix = os.path.join(tools_dir, 'testing', 'bin')
+  if IsWindows():
+    return os.path.join(dart_binary_prefix, 'windows', 'dart.exe')
+  else:
+    return os.path.join(dart_binary_prefix, GuessOS(), 'dart')
+
+
 if __name__ == "__main__":
   import sys
   Main(sys.argv)