[telemetry] Sort imports in Telemetry and its dependents.

tools/perf/metrics/system_memory.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.
 
+from telemetry.value import scalar
+
 from metrics import memory
 from metrics import Metric
-from telemetry.value import scalar
 
 
 class SystemMemoryMetric(Metric):
   """SystemMemoryMetric gathers system memory statistic.
 
   This metric collects system memory stats per test.  It reports the difference
   (delta) in system memory starts from the start of the test to the end of it.
   """
 
   def __init__(self, browser):
@@ skipping 97 matching lines @@
       memory_stats[process_type] = end_process_memory - start_value
     else:
       for metric in end_process_memory:
         end_value = end_process_memory[metric]
         start_value = start_memory_stats[process_type][metric] or 0
         if 'Peak' in metric:
           memory_stats[process_type][metric] = end_value
         else:
           memory_stats[process_type][metric] = end_value - start_value
   return memory_stats