Telemetry: make media perf tests log errors rather than timing out

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 16 matching lines @@
     """Create the media metrics for all media elements in the document."""
     if hasattr(page, 'skip_basic_metrics'):
       self._skip_basic_metrics = page.skip_basic_metrics
     tab.ExecuteJavaScript('window.__createMediaMetricsForDocument()')
 
   def Stop(self, page, tab):
     self._results = tab.EvaluateJavaScript('window.__getAllMetrics()')
 
   def AddResults(self, tab, results):
     """Reports all recorded metrics as Telemetry perf results."""
-    assert self._results
     trace_names = []
     for media_metric in self._results:
       trace_names.append(self._AddResultsForMediaElement(media_metric, results))
 
     return '_'.join(trace_names) or tab.url
 
   def _AddResultsForMediaElement(self, media_metric, results):
     """Reports metrics for one media element.
 
     Media metrics contain an ID identifying the media element and values:
@@ skipping 23 matching lines @@
       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')
     return trace