Improve readability of power monitoring code and add additional

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

Index: tools/telemetry/telemetry/internal/platform/power_monitor/android_temperature_monitor.py
diff --git a/tools/telemetry/telemetry/internal/platform/power_monitor/android_temperature_monitor.py b/tools/telemetry/telemetry/internal/platform/power_monitor/android_temperature_monitor.py
index 436dac47cf27f8a642aaf7238cd5796303808257..ebf5774eb44e1fe8b96d5c2eb7e8654d6a631288 100644
--- a/tools/telemetry/telemetry/internal/platform/power_monitor/android_temperature_monitor.py
+++ b/tools/telemetry/telemetry/internal/platform/power_monitor/android_temperature_monitor.py
@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import logging
+
 from telemetry.internal.platform import power_monitor
 
 try:
@@ -25,35 +27,26 @@ class AndroidTemperatureMonitor(power_monitor.PowerMonitor):
     return self._GetBoardTemperatureCelsius() is not None
 
   def StartMonitoringPower(self, browser):
+    # don't call _CheckStart() because this is temperature, not power
+    # therefore, StartMonitoringPower and StopMonitoringPower
+    # do not need to be paired
     pass
 
   def StopMonitoringPower(self):
-    power_data = {'identifier': 'android_temperature_monitor'}
-
-    # Take the current temperature as average based on the assumption that the
-    # temperature changes slowly during measurement time.
-    average_temperature = self._GetBoardTemperatureCelsius()
-    if average_temperature is None:
-      return power_data
-
-    # Insert temperature into the appropriate position in the dictionary
-    # returned by StopMonitoringPower() creating appropriate sub-dictionaries on
-    # the way if necessary.
-    temperature_path = [
-        'platform_info', 'average_temperature_c']
-    temperature_insertion_point = power_data
-    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
+    avg_temp = self._GetBoardTemperatureCelsius()
+    if avg_temp is None:
+      return {'identifier': 'android_temperature_monitor'}
+    else:
+      return {'identifier': 'android_temperature_monitor',
+              'platform_info': {'average_temperature_c': avg_temp}}
 
   def _GetBoardTemperatureCelsius(self):
     try:
       contents = self._device.ReadFile(_TEMPERATURE_FILE)
       return float(contents) if contents else None
+    except ValueError:
+      logging.warning('String returned from device.ReadFile(_TEMPERATURE_FILE) '
+                      'in invalid format.')
+      return None
     except device_errors.CommandFailedError:
       return None