Reland of Migrate DeviceUtils.ReadFile to adb_wrapper (try 3)

tools/telemetry/telemetry/core/platform/power_monitor/android_temperature_monitor.py

 # Copyright 2014 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 telemetry.core.platform.power_monitor as power_monitor
+from telemetry.core import util
+from telemetry.core.platform import power_monitor
+
+util.AddDirToPythonPath(util.GetChromiumSrcDir(), 'build', 'android')
+try:
+  from pylib.device import device_errors  # pylint: disable=F0401
+except ImportError:
+  device_errors = None
+
 
 _TEMPERATURE_FILE = '/sys/class/thermal/thermal_zone0/temp'
 
 
 class AndroidTemperatureMonitor(power_monitor.PowerMonitor):
   """
   Delegates monitoring to another PowerMonitor and adds temperature measurements
   to overall results.
   """
   def __init__(self, monitor, device):
@@ skipping 34 matching lines @@
     for path_element in temperature_path[:-1]:
       if not path_element in temperature_insertion_point:
         temperature_insertion_point[path_element] = {}
       temperature_insertion_point = temperature_insertion_point[path_element]
     assert temperature_path[-1] not in temperature_insertion_point
     temperature_insertion_point[temperature_path[-1]] = average_temperature
 
     return power_data
 
   def _GetBoardTemperatureCelsius(self):
-    contents = self._device.ReadFile(_TEMPERATURE_FILE)
-    if len(contents) > 0:
-      return float(contents[0])
-    return None
+    try:
+      contents = self._device.ReadFile(_TEMPERATURE_FILE)
+      return float(contents) if contents else None
+    except device_errors.CommandFailedError:
+      return None