Adds proxy pingback chromedriver integration test (testPingback).

tools/chrome_proxy/webdriver/smoke.py

 # Copyright 2017 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 common
 from common import TestDriver
 from common import IntegrationTest
 
 
 class Smoke(IntegrationTest):
@@ skipping 13 matching lines @@
       t.AddChromeArg('--enable-spdy-proxy-auth')
       t.AddChromeArg('--enable-quic')
       t.AddChromeArg('--data-reduction-proxy-http-proxies=https://proxy.googlezip.net:443')
       t.AddChromeArg('--force-fieldtrials=DataReductionProxyUseQuic/Enabled')
       t.LoadURL('http://check.googlezip.net/test.html')
       responses = t.GetHTTPResponses()
       self.assertEqual(2, len(responses))
       for response in responses:
         self.assertHasChromeProxyViaHeader(response)
 
+  # Ensure pageload metric pingback with DataSaver.
+  def testPingback(self):
+    with TestDriver() as t:
+      t.AddChromeArg('--enable-spdy-proxy-auth')
+      t.AddChromeArg('--enable-data-reduction-proxy-force-pingback')
+      t.LoadURL('http://check.googlezip.net/test.html')
+      t.LoadURL('http://check.googlezip.net/test.html')
+      t.SleepUntilHistogramHasEntry("DataReductionProxy.Pingback.Succeeded")
+      # Verify one pingback attempt that was successful.
+      attempted = t.GetHistogram('DataReductionProxy.Pingback.Attempted')
+      self.assertEqual(1, attempted['count'])
+      succeeded = t.GetHistogram('DataReductionProxy.Pingback.Succeeded')
+      self.assertEqual(1, succeeded['count'])
+
 if __name__ == '__main__':
   IntegrationTest.RunAllTests()