Enable presubmit pylint in build/android.

build/android/pylib/perf/surface_stats_collector.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 Queue
 import datetime
 import logging
 import re
 import threading
 
@@ skipping 53 matching lines @@
 
   def SampleResults(self):
     self._StorePerfResults()
     results = self.GetResults()
     self._results = []
     return results
 
   def GetResults(self):
     return self._results or self._GetEmptyResults()
 
-  def _GetEmptyResults(self):
+  @staticmethod
+  def _GetEmptyResults():
     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, min_normalized_delta=None):
@@ skipping 10 matching lines @@
     seconds = timestamps[-1] - timestamps[0]
 
     frame_lengths, normalized_frame_lengths = \
         SurfaceStatsCollector._GetNormalizedDeltas(
             timestamps, refresh_period, _MIN_NORMALIZED_FRAME_LENGTH)
     if len(frame_lengths) < frame_count - 1:
       logging.warning('Skipping frame lengths that are too short.')
       frame_count = len(frame_lengths) + 1
     if len(frame_lengths) == 0:
       raise Exception('No valid frames lengths found.')
-    length_changes, normalized_changes = \
+    _length_changes, normalized_changes = \
         SurfaceStatsCollector._GetNormalizedDeltas(
             frame_lengths, refresh_period)
     jankiness = [max(0, round(change)) for change in normalized_changes]
     pause_threshold = 20
     jank_count = sum(1 for change in jankiness
                      if change > 0 and change < pause_threshold)
     return [
         SurfaceStatsCollector.Result(
             'avg_surface_fps' + result_suffix,
             int(round((frame_count - 1) / seconds)), 'fps'),
@@ skipping 182 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(),
     }