Migrate dartium_tools from chrome branch to dart repo

tools/dartium/fetch_reference_build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2014 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.
 
 """Fetches an archived chromium build into
   src/chrome/tools/test/reference_build unless
   src/chrome/tools/test/reference_build/REQUESTED_REVISION is the same as
   src/chrome/tools/test/reference_build/CURRENT_REVISION.
   Must be run from the root of a Dartium or multivm checkout.
 
 Usage:
-  $ ./src/dart/tools/bots/fetch_reference_build_revision.py
+  $ ./src/dart/tools/dartium/fetch_reference_build_revision.py
 """
 
 import os
 import subprocess
 import sys
 
 def main(argv):
   dirname = os.path.join('src', 'chrome', 'tools',
                         'test', 'reference_build')
   request = os.path.join(dirname, 'REQUESTED_REVISION')
   found = os.path.join(dirname, 'CURRENT_REVISION')
   if not os.path.exists(request):
     return
   with file(request, 'r') as f:
     request_revision = f.read()
 
   if os.path.exists(found):
     with file(found, 'r') as f:
       found_revision = f.read()
     if found_revision == request_revision:
       return
 
   get_script = os.path.join('src', 'dart', 'tools',
-                            'bots', 'get_chromium_build.py')
+                            'dartium', 'get_chromium_build.py')
   get_script = os.path.abspath(get_script)
   exit_code = subprocess.call(['python', get_script,
                                '-r', request_revision,
                                '-t', dirname])
   if exit_code == 0:
     with file(found, 'w') as f:
       f.write(request_revision)
   return exit_code
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))