[telemetry] Sort imports in Telemetry and its dependents.

tools/perf/metrics/keychain_metric.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 sys
 
-from metrics import Metric
 from telemetry.util.mac import keychain_helper
 from telemetry.value import histogram_util
 from telemetry.value import scalar
 
+from metrics import Metric
+
 
 class KeychainMetric(Metric):
   """KeychainMetric gathers keychain statistics from the browser object.
 
   This includes the number of times that the keychain was accessed.
   """
 
   DISPLAY_NAME = 'OSX_Keychain_Access'
   HISTOGRAM_NAME = 'OSX.Keychain.Access'
 
@@ skipping 42 matching lines @@
     """Adds the number of times that the keychain was accessed to |results|.
     Has no effect on non-Mac platforms."""
     if sys.platform != 'darwin':
       return
 
     access_count = histogram_util.GetHistogramSum(
         histogram_util.BROWSER_HISTOGRAM, KeychainMetric.HISTOGRAM_NAME, tab)
     results.AddValue(scalar.ScalarValue(
         results.current_page, KeychainMetric.DISPLAY_NAME, 'count',
         access_count))