clovis: Report the number and cost of DNS requests.

tools/android/loading/metrics_unittest.py

Index: tools/android/loading/metrics_unittest.py
diff --git a/tools/android/loading/metrics_unittest.py b/tools/android/loading/metrics_unittest.py
index 56153bf2050ace135f22e8a4dffbe8ded87548db..236b48aa792e7b658617aca94be0f1c036fdc199 100644
--- a/tools/android/loading/metrics_unittest.py
+++ b/tools/android/loading/metrics_unittest.py
@@ -72,6 +72,18 @@ class MetricsTestCase(unittest.TestCase):
     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))