backport code cleanup for power monitoring to m48

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

Index: tools/telemetry/telemetry/internal/platform/power_monitor/cros_power_monitor.py
diff --git a/tools/telemetry/telemetry/internal/platform/power_monitor/cros_power_monitor.py b/tools/telemetry/telemetry/internal/platform/power_monitor/cros_power_monitor.py
index 586a2985682718a4c1f7d7d9d32b7b5903556fb2..7f922bd56ffa8b2fa25ceaf53fd27cede8aba2d5 100644
--- a/tools/telemetry/telemetry/internal/platform/power_monitor/cros_power_monitor.py
+++ b/tools/telemetry/telemetry/internal/platform/power_monitor/cros_power_monitor.py
@@ -33,7 +33,7 @@ class CrosPowerMonitor(sysfs_power_monitor.SysfsPowerMonitor):
     return super(CrosPowerMonitor, self).CanMonitorPower()
 
   def StartMonitoringPower(self, browser):
-    self._CheckStart()
+    super(CrosPowerMonitor, self).StartMonitoringPower(browser)
     if self._IsOnBatteryPower():
       sample = self._platform.RunCommand(['dump_power_status;', 'date', '+%s'])
       self._initial_power, self._start_time = CrosPowerMonitor.SplitSample(
@@ -43,7 +43,7 @@ class CrosPowerMonitor(sysfs_power_monitor.SysfsPowerMonitor):
                       'Results may be incorrect.')
 
   def StopMonitoringPower(self):
-    self._CheckStop()
+    # Don't need to call self._CheckStop here; it's called by the superclass
     cpu_stats = super(CrosPowerMonitor, self).StopMonitoringPower()
     power_stats = {}
     if self._IsOnBatteryPower():