[Telemetry] Report network metrics for the page cycler.

tools/perf/metrics/network.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.
+
+import json
+
+from metrics import Metric
+
+_COUNTER_TO_RESULTS = {
+    'tcp.read_bytes':               ('tcp_read_bytes',    'bytes'),
+    'tcp.write_bytes':              ('tcp_write_bytes',   'bytes'),
+    'HttpNetworkTransaction.Count': ('num_requests',      'count'),
+    'tcp.connect':                  ('num_connects',      'count'),
+    'spdy.sessions':                ('num_spdy_sessions', 'count'),
+    }
+
+class NetworkMetric(Metric):
+  """A metric for network information."""
+
+  def __init__(self):
+    super(NetworkMetric, self).__init__()
+    self._results = None
+
+  def _GetCounters(self, tab):
+    return tab.EvaluateJavaScript("""
+(function(counters) {
+  var results = {};
+  if (!window.chrome || !window.chrome.benchmarking)
+    return results;
+  for (var i = 0; i < counters.length; i++)
+    results[counters[i]] = chrome.benchmarking.counter(counters[i]);
+  return results;
+})(%s);
+""" % json.dumps(_COUNTER_TO_RESULTS.keys()))
+
+  def Start(self, page, tab):
+    assert not self._results, 'Must AddResults() before calling Start() again.'
+    self._results = self._GetCounters(tab)
+
+  def Stop(self, page, tab):
+    assert self._results, 'Must Start() before Stop().'
+    results = self._GetCounters(tab)
+    for counter in self._results:
+      self._results[counter] = results[counter] - self._results[counter]
+
+  def AddResults(self, tab, results):
+    assert self._results, 'Must Start() and Stop() before AddResults().'
+    for counter, trace_unit in _COUNTER_TO_RESULTS.iteritems():
+      if counter not in self._results:
+        continue
+      results.Add(trace_unit[0], trace_unit[1], self._results[counter],
+                  data_type='unimportant')
+    self._results = None