Telemetry CPU metric trace names are misleading

tools/perf/metrics/cpu.py

 # Copyright 2013 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 metrics import Metric
 
 class CpuMetric(Metric):
   """Calulates CPU load over a span of time."""
 
   def __init__(self, browser):
@@ skipping 12 matching lines @@
   def Stop(self, page, tab):
     assert self._start_cpu, 'Must call Start() first'
     self._results = _SubtractCpuStats(self._browser.cpu_stats, self._start_cpu)
 
   # Optional argument trace_name is not in base class Metric.
   # pylint: disable=W0221
   def AddResults(self, tab, results, trace_name='cpu_utilization'):
     assert self._results, 'Must call Stop() first'
     # Add a result for each process type.
     for process_type in self._results:
-      trace_name = '%s_%s' % (trace_name, process_type.lower())
+      trace_name_for_process = '%s_%s' % (trace_name, process_type.lower())
       cpu_percent = 100 * self._results[process_type]
-      results.Add(trace_name, '%', cpu_percent, chart_name='cpu_utilization',
-                  data_type='unimportant')
+      results.Add(trace_name_for_process, '%', cpu_percent,
+                  chart_name='cpu_utilization', data_type='unimportant')
 
 
 def _SubtractCpuStats(cpu_stats, start_cpu_stats):
   """Computes average cpu usage over a time period for different process types.
 
   Each of the two cpu_stats arguments is a dict with the following format:
       {'Browser': {'CpuProcessTime': ..., 'TotalTime': ...},
        'Renderer': {'CpuProcessTime': ..., 'TotalTime': ...}
        'Gpu': {'CpuProcessTime': ..., 'TotalTime': ...}}
 
@@ skipping 12 matching lines @@
     if (not cpu_stats[process_type]) or (not start_cpu_stats[process_type]):
       continue
     cpu_process_time = (cpu_stats[process_type]['CpuProcessTime'] -
                         start_cpu_stats[process_type]['CpuProcessTime'])
     total_time = (cpu_stats[process_type]['TotalTime'] -
                   start_cpu_stats[process_type]['TotalTime'])
     assert total_time > 0, 'Expected total_time > 0, was: %d' % total_time
     cpu_usage[process_type] = float(cpu_process_time) / total_time
   return cpu_usage