Fix name/path separator for telemetry_unittests test names (src-side)

This ports https://codereview.chromium.org/674023002 to src-side script.

BUG=399371, 425694, 422235
R=sergiyb@chromium.org

Review URL: https://codereview.chromium.org/677393002

Cr-Commit-Position: refs/heads/master@{#301351}

testing/scripts/common.py

@@ -65,13 +65,13 @@ def temporary_file():
     os.remove(path)
 
 
-def parse_common_test_results(json_results):
+def parse_common_test_results(json_results, test_separator='/'):
   def convert_trie_to_flat_paths(trie, prefix=None):
     # Also see webkitpy.layout_tests.layout_package.json_results_generator
     result = {}
     for name, data in trie.iteritems():
       if prefix:
-        name = prefix + '/' + name
+        name = prefix + test_separator + name
       if len(data) and not 'actual' in data and not 'expected' in data:
         result.update(convert_trie_to_flat_paths(data, name))
       else:

testing/scripts/telemetry_unittests.py

@@ -40,7 +40,7 @@ def main_run(args):
     with open(tempfile_path) as f:
       results = json.load(f)
 
-  parsed_results = common.parse_common_test_results(results)
+  parsed_results = common.parse_common_test_results(results, test_separator='.')
   failures = parsed_results['unexpected_failures']
 
   json.dump({