Make Data Saver integration test use new secure proxy check URL flag.

The flag for specifying the URL for the Data Saver secure proxy check
was changed in https://codereview.chromium.org/961983002/. This change
makes the relevant integration test use the new flag value, and also
makes the test restart after each page.

BUG=463210

Review URL: https://codereview.chromium.org/971073002

Cr-Commit-Position: refs/heads/master@{#318923}

tools/chrome_proxy/integration_tests/chrome_proxy_measurements.py

@@ -205,17 +205,17 @@ class ChromeProxyHTTPFallbackProbeURL(ChromeProxyValidation):
   """
 
   def __init__(self):
-    super(ChromeProxyHTTPFallbackProbeURL, self).__init__()
+    super(ChromeProxyHTTPFallbackProbeURL, self).__init__(
+        restart_after_each_page=True)
 
   def CustomizeBrowserOptions(self, options):
     super(ChromeProxyHTTPFallbackProbeURL,
           self).CustomizeBrowserOptions(options)
     # Use the test server probe URL which returns the response
     # body as specified by respBody.
-    probe_url = GetResponseOverrideURL(
-        respBody='not OK')
+    probe_url = GetResponseOverrideURL(respBody='not OK')
     options.AppendExtraBrowserArgs(
-        '--data-reduction-proxy-probe-url=%s' % probe_url)
+        '--data-reduction-proxy-secure-proxy-check-url=%s' % probe_url)
 
   def AddResults(self, tab, results):
     self._metrics.AddResultsForHTTPFallback(tab, results)