[Telemetry] Close msr server win after checking whether platform can monitor power.

tools/telemetry/telemetry/internal/platform/power_monitor/msr_power_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 logging
 import platform
 import re
 
 from telemetry import decorators
 from telemetry.internal.platform import power_monitor
@@ skipping 115 matching lines @@
 
 
 class MsrPowerMonitorWin(MsrPowerMonitor):
   def CanMonitorPower(self):
     family, model = map(int, re.match('.+ Family ([0-9]+) Model ([0-9]+)',
                         platform.processor()).groups())
     if not _IsSandyBridgeOrLater(platform.processor(), family, model):
       logging.info('Cannot monitor power: pre-Sandy Bridge CPU.')
       return False
 
-    return self._CheckMSRs()
+    msr_return_value = self._CheckMSRs()
+    # Since _CheckMSRs() start the MSR server, we must close it after checking

[dtu, 2015/11/09 18:13:24]

nit: starts

[nednguyen, 2015/11/09 18:16:44]

Done.

+    # to avoid leaking msr server process.
+    self._backend.CloseMsrServer()

[dtu, 2015/11/09 18:13:25]

We need to do so on both Linux and Win, so perhaps it's better inside
_CheckMSRs().

[nednguyen, 2015/11/09 18:16:44]

CloseMsrServer is win_platform_backend only, updated the comment to reflect
this.

[dtu, 2015/11/09 18:25:46]

Ah, yes, your'e right.

+    return msr_return_value
+
 
   def StopMonitoringPower(self):
     power_statistics = super(MsrPowerMonitorWin, self).StopMonitoringPower()
     self._backend.CloseMsrServer()
     return power_statistics