[build/android] Load/dump pickles directly form/to files

build/android/pylib/perf/perf_test_instance.py

 # Copyright 2016 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 json
 import logging
 import os
 import pickle
 import re
 
 from devil import base_error
 from devil.utils import cmd_helper
 from pylib import constants
 from pylib.base import base_test_result
 from pylib.base import test_instance
 from pylib.constants import host_paths
 
 
 _GIT_CR_POS_RE = re.compile(r'^Cr-Commit-Position: refs/heads/master@{#(\d+)}$')
 
 
 def _GetPersistedResult(test_name):
   file_name = os.path.join(constants.PERF_OUTPUT_DIR, test_name)
   if not os.path.exists(file_name):
     logging.error('File not found %s', file_name)
     return None
 
   with file(file_name, 'r') as f:
-    return pickle.loads(f.read())
+    return pickle.load(f)
 
 
 def _GetChromiumRevision():
   # pylint: disable=line-too-long
   """Get the git hash and commit position of the chromium master branch.
 
   See:
   https://chromium.googlesource.com/chromium/tools/build/+/387e3cf3/scripts/slave/runtest.py#211
 
   Returns:
@@ skipping 223 matching lines @@
 
   @property
   def test_filter(self):
     return self._test_filter
 
 
 class PersistentDataError(base_error.BaseError):
   def __init__(self, message):
     super(PersistentDataError, self).__init__(message)
     self._is_infra_error = True