[Bisect] Account for tir_label-level summaries in parse_metric

scripts/slave/recipe_modules/bisect_tester/parse_metric.py

 import math
 import re
 from functools import reduce
 
 
 def _geom_mean_and_std_dev_from_histogram(histogram):  # pragma: no cover
   # Copied from: https://code.google.com/p/chromium/codesearch#chromium/build/scripts/common/chromium_utils.py&l=222
   # TODO(robertocn): Remove this code duplication from common.chromium_utils
   if not 'buckets' in histogram:
     return 0.0, 0.0
@@ skipping 39 matching lines @@
     trace_name = 'summary'
   try:
     for chart in results['charts']:
       if escape_chars(chart) == chart_name:
         chart_name = chart  # Unescaping
         break
     for trace in results['charts'][chart_name]:
       if escape_chars(trace) == trace_name:
         trace_name = trace  # Unescaping
         break
+
+    # This can happen if trace_name is meant to be a tir_label. This workaround
+    # is necessary because test paths are ambiguous, such that a 2-part test
+    # name can represent a tir_label-level summary or a story-level summary.
+    if trace_name not in results['charts'].get(chart_name, {}):
+      chart_name = trace_name + '@@' + chart_name
+      trace_name = 'summary'
+
     if (results['charts'][chart_name][trace_name]['type'] ==
         'list_of_scalar_values'):
       values = results['charts'][chart_name][trace_name]['values']
       if values:
         avg_value = [sum(values) / len(values)]
         return True, avg_value, results
     if results['charts'][chart_name][trace_name]['type'] == 'histogram':
       return True, [_geom_mean_and_std_dev_from_histogram(
           results['charts'][chart_name][trace_name])[0]], results
   except KeyError:  # e.g. metric not found
@@ skipping 104 matching lines @@
         histogram_values = eval(current_line)
 
         for b in histogram_values['buckets']:
           average_for_bucket = float(b['high'] + b['low']) * 0.5
           # Extends the list with N-elements with the average for that bucket.
           values_list.extend([average_for_bucket] * b['count'])
       except Exception:
         pass
 
   return values_list