clovis: Report the number and cost of DNS requests.

tools/android/loading/metrics_unittest.py

 # Copyright 2016 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 copy
 import unittest
 
 import metrics
 import request_track
 import test_utils
@@ skipping 54 matching lines @@
         self._BODY_SIZE + self._RESPONSE_HEADERS_SIZE + cache_control_length,
         downloaded)
 
   def testTransferSize(self):
     trace = self._MakeTrace()
     r = trace.request_track.GetEvents()[0]
     (_, downloaded) = metrics.TransferSize([r])
     self.assertEqual(self._BODY_SIZE + self._RESPONSE_HEADERS_SIZE,
                      downloaded)
 
+  def testDnsRequestsAndCost(self):
+    trace = self._MakeTrace()
+    (count, cost) = metrics.DnsRequestsAndCost(trace)
+    self.assertEqual(0, count)
+    self.assertEqual(0, cost)
+    r = trace.request_track.GetEvents()[0]
+    r.timing.dns_end = 12
+    r.timing.dns_start = 4
+    (count, cost) = metrics.DnsRequestsAndCost(trace)
+    self.assertEqual(1, count)
+    self.assertEqual(8, cost)
+
   @classmethod
   def _MakeTrace(cls):
     request = request_track.Request.FromJsonDict(copy.deepcopy(cls._REQUEST))
     return test_utils.LoadingTraceFromEvents([request])
 
 
 if __name__ == '__main__':
   unittest.main()