[Telemetry + tools/perf] Modify the pylint disable message to use symbolic name

tools/telemetry/telemetry/internal/platform/mac_platform_backend_unittest.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 os
 import unittest
 
 from telemetry.core import platform as platform_module
 from telemetry.core import os_version
 from telemetry import decorators
 
 
 class MacPlatformBackendTest(unittest.TestCase):
   def testVersionCamparison(self):
     self.assertGreater(os_version.YOSEMITE, os_version.MAVERICKS)
     self.assertGreater(os_version.MAVERICKS, os_version.SNOWLEOPARD)
     self.assertGreater(os_version.LION, os_version.LEOPARD)
     self.assertEqual(os_version.YOSEMITE, 'yosemite')
     self.assertEqual(os_version.MAVERICKS, 'mavericks')
     self.assertEqual('%s2' % os_version.MAVERICKS, 'mavericks2')
     self.assertEqual(''.join([os_version.MAVERICKS, '2']),
                      'mavericks2')
     self.assertEqual(os_version.LION.upper(), 'LION')
 
   @decorators.Enabled('mac')
   def testGetCPUStats(self):
     platform = platform_module.GetHostPlatform()
 
-    backend = platform._platform_backend # pylint: disable=W0212
+    backend = platform._platform_backend # pylint: disable=protected-access
 
     cpu_stats = backend.GetCpuStats(os.getpid())
     self.assertGreater(cpu_stats['CpuProcessTime'], 0)
     self.assertTrue(cpu_stats.has_key('ContextSwitches'))
     if backend.GetOSVersionName() >= os_version.MAVERICKS:
       self.assertTrue(cpu_stats.has_key('IdleWakeupCount'))