[Android] Add optional per-test cooling wait for perf tests.

build/android/pylib/device/battery_utils.py

 # Copyright 2015 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.
 
 """Provides a variety of device interactions with power.
 """
 # pylint: disable=unused-argument
 
 import collections
 import contextlib
@@ skipping 437 matching lines @@
     """
     def cool_device():
       temp = self.GetBatteryInfo().get('temperature')
       if temp is None:
         logging.warning('Unable to find current battery temperature.')
         temp = 0
       else:
         logging.info('Current battery temperature: %s', temp)
       return int(temp) <= target_temp
 
-    logging.info('Waiting for the device to cool down to %s degrees.',
+    logging.info('Waiting for the device to cool down to %s (0.1 C)',
                  target_temp)
     timeout_retry.WaitFor(cool_device, wait_period=wait_period)
 
   @decorators.WithTimeoutAndRetriesFromInstance()
   def TieredSetCharging(self, enabled, timeout=None, retries=None):
     """Enables or disables charging on the device.
 
     Args:
       enabled: A boolean indicating whether charging should be enabled or
         disabled.
@@ skipping 102 matching lines @@
     self._cache['profile'] = {
         'name': None,
         'witness_file': None,
         'enable_command': None,
         'disable_command': None,
         'charge_counter': None,
         'voltage': None,
         'current': None,
     }
     return False