[Bisect] Account for tir_label-level summaries in parse_metric

scripts/slave/recipe_modules/auto_bisect/config_validation_test.py

 #!/usr/bin/env python
 # Copyright 2016 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.
 
 import copy
 import os
 import sys
 import unittest
 
@@ skipping 90 matching lines @@
     with self.assertRaises(config_validation.ValidationFail):
       config_validation.validate_bisect_config(config, schema)
 
   def test_validate_metric_format_failure(self):
     schema = {
         'metric': {'type': 'string'},
         'bisect_mode': {'type': 'string'},
     }
     config = {
         'bisect_mode': 'mean',
-        'metric': 'a/b/c',
+        'metric': 'a/b/c/d',
     }
     with self.assertRaises(config_validation.ValidationFail):
       config_validation.validate_bisect_config(config, schema)
 
   def test_validate_metric_format_pass(self):
     schema = {
         'metric': {'type': 'string'},
         'bisect_mode': {'type': 'string'},
     }
     config = {
@@ skipping 46 matching lines @@
   def test_validate_choice_failure(self):
     with self.assertRaises(config_validation.ValidationFail):
       config_validation.validate_key(
           config={'x': 3},
           schema={'x': {'type': 'int', 'choices': [1, 2]}},
           key='x')
 
 
 if __name__ == '__main__':
   unittest.main()  # pragma: no cover