Update observatory_tool.py to remove package-root

tools/bots/bot.py

 #!/usr/bin/python
 
 # 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.
 
 """
 Shared code for use in the buildbot scripts.
 """
 
@@ skipping 237 matching lines @@
 def RunTestRunner(build_info, path):
   """
   Runs the test package's runner on the package at 'path'.
   """
   sdk_bin = os.path.join(
       bot_utils.DART_DIR,
       utils.GetBuildSdkBin(BUILD_OS, build_info.mode, build_info.arch))
 
   build_root = utils.GetBuildRoot(
       BUILD_OS, build_info.mode, build_info.arch)
-  package_root = os.path.abspath(os.path.join(build_root, 'packages'))
 
   dart_name = 'dart.exe' if build_info.system == 'windows' else 'dart'
   dart_bin = os.path.join(sdk_bin, dart_name)
 
   test_bin = os.path.abspath(
       os.path.join('third_party', 'pkg', 'test', 'bin', 'test.dart'))
 
   with utils.ChangedWorkingDirectory(path):
-    args = [dart_bin, '--package-root=' + package_root, test_bin,
-            '--package-root', package_root, '--reporter', 'expanded',
-            '--no-color']
+    args = [dart_bin, test_bin, '--reporter', 'expanded', '--no-color']
     print("Running %s" % ' '.join(args))
     RunProcess(args)
 
 
 def RunProcess(command, env=None):
   """
   Runs command.
 
   If a non-zero exit code is returned, raises an OSError with errno as the exit
   code.
   """
   if env is None:
     no_color_env = dict(os.environ)
   else:
     no_color_env = env
   no_color_env['TERM'] = 'nocolor'
 
   exit_code = subprocess.call(command, env=no_color_env)
   if exit_code != 0:
     raise OSError(exit_code)
 
 
 def GetStepName(name, flags):
   """
   Filters out flags with '=' as this breaks the /stats feature of the buildbot.
   """
   flags = [x for x in flags if not '=' in x]
   return ('%s tests %s' % (name, ' '.join(flags))).strip()