Android / Telemetry: make surface_stats_collector more robust.

build/android/pylib/surface_stats_collector.py

 # Copyright (c) 2012 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 Queue
 import datetime
 import logging
 import re
 import threading
 
@@ skipping 46 matching lines @@
 
   def Stop(self):
     self._StorePerfResults()
     if self._collector_thread:
       self._stop_event.set()
       self._collector_thread.join()
       self._collector_thread = None
 
   def SampleResults(self):
     self._StorePerfResults()
-    results = self._results
+    results = self.GetResults()
     self._results = []
     return results
 
   def GetResults(self):
-    return self._results
+    return self._results or self._GetEmptyResults()
+
+  def _GetEmptyResults(self):
+    return [
+        SurfaceStatsCollector.Result('refresh_period', None, 'seconds'),
+        SurfaceStatsCollector.Result('jank_count', None, 'janks'),
+        SurfaceStatsCollector.Result('max_frame_delay', None, 'vsyncs'),
+        SurfaceStatsCollector.Result('frame_lengths', None, 'vsyncs'),
+        SurfaceStatsCollector.Result('avg_surface_fps', None, 'fps')
+    ]
 
   @staticmethod
   def _GetNormalizedDeltas(data, refresh_period):
     deltas = [t2 - t1 for t1, t2 in zip(data, data[1:])]
     return (deltas, [delta / refresh_period for delta in deltas])
 
   def _StorePerfResults(self):
     if self._use_legacy_method:
       surface_after = self._GetSurfaceStatsLegacy()
       td = surface_after['timestamp'] - self._surface_before['timestamp']
@@ skipping 172 matching lines @@
       try:
         cur_surface = int(match.group(1), 16)
       except Exception:
         logging.error('Failed to parse current surface from ' + match.group(1))
     else:
       logging.warning('Failed to call SurfaceFlinger surface ' + results[0])
     return {
         'page_flip_count': cur_surface,
         'timestamp': datetime.datetime.now(),
     }