No need to cast to str in media metric results.

tools/perf/metrics/media.py

 # Copyright 2013 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 logging
 import os
 
 from metrics import Metric
 
 
 class MediaMetric(Metric):
@@ skipping 38 matching lines @@
           'decoded_bytes': 13233,
           ...
       }
     }
     """
     def AddOneResult(metric, unit):
       metrics = media_metric['metrics']
       for m in metrics:
         if m.startswith(metric):
           special_label = m[len(metric):]
-          results.Add(trace + special_label, unit, str(metrics[m]),
+          results.Add(trace + special_label, unit, metrics[m],
                       chart_name=metric, data_type='default')
 
     trace = media_metric['id']
     if not trace:
       logging.error('Metrics ID is missing in results.')
       return
 
     if not self._skip_basic_metrics:
       AddOneResult('buffering_time', 'ms')
       AddOneResult('decoded_audio_bytes', 'bytes')
       AddOneResult('decoded_video_bytes', 'bytes')
       AddOneResult('decoded_frame_count', 'frames')
       AddOneResult('dropped_frame_count', 'frames')
       AddOneResult('time_to_play', 'ms')
 
     AddOneResult('avg_loop_time', 'ms')
     AddOneResult('seek', 'ms')