Added Data Saver ChromeDriver test for via header fallback logic.

tools/chrome_proxy/webdriver/bypass.py

Index: tools/chrome_proxy/webdriver/bypass.py
diff --git a/tools/chrome_proxy/webdriver/bypass.py b/tools/chrome_proxy/webdriver/bypass.py
index 3b7798ae6c16c719aacbf11045b8b13656ca37da..ef5ecde4b4ebc1729b297a4336822d171cf47b7a 100644
--- a/tools/chrome_proxy/webdriver/bypass.py
+++ b/tools/chrome_proxy/webdriver/bypass.py
@@ -102,6 +102,68 @@ class Bypass(IntegrationTest):
       for response in responses:
         self.assertHasChromeProxyViaHeader(response)
 
+  # Verify that when Chrome receives a 4xx response through a Data Reduction
+  # Proxy that doesn't set a proper via header, Chrome bypasses all proxies and
+  # retries the request over direct.
+  def testMissingViaHeader4xxBypass(self):

[megjablon, 2017/03/11 00:51:47]

Isn't this the ChromeProxyHTTPToDirectFallback telemetry test? Is there another
bug for this? Or at least the bug linked looks like it's just for a fallback
test.

[sclittle, 2017/03/11 01:29:03]

The non-4xx test below is the counterpart for the
ChromeProxyHTTPFallbackViaHeader test, I think that's the one linked to by the
bug:
https://cs.chromium.org/chromium/src/tools/chrome_proxy/integration_tests/chr...

Good point though, I don't think the 4xx via header bypass behavior had a
telemetry counterpart, so the linked bug isn't really related to it. I'll create
a separate bug and CL for the 4xx test, and have this CL just include the test
for the non-4xx fallback behavior.

+    with TestDriver() as test_driver:
+      test_driver.AddChromeArg('--enable-spdy-proxy-auth')
+
+      # Set the primary Data Reduction Proxy to be the test server, which does
+      # not add any Via headers.
+      test_driver.AddChromeArg('--data-reduction-proxy-http-proxies='
+                               'http://chromeproxy-test.appspot.com;'
+                               'http://compress.googlezip.net')
+
+      # Load a page that will come back with a 4xx response code and without the
+      # proper via header. Chrome should bypass all proxies and retry the
+      # request.
+      test_driver.LoadURL(
+          'http://chromeproxy-test.appspot.com/default?respStatus=414')
+      responses = test_driver.GetHTTPResponses()
+      self.assertNotEqual(0, len(responses))
+      for response in responses:
+        self.assertNotHasChromeProxyViaHeader(response)
+
+      # Check that the BlockTypePrimary histogram has a single entry in the
+      # MissingViaHeader4xx category (which is enum value 4), to make sure that
+      # the bypass was caused by the missing via header logic and not something
+      # else.
+      histogram = test_driver.GetHistogram(
+          "DataReductionProxy.BlockTypePrimary")
+      self.assertEqual(1, histogram['count'])
+      self.assertIn({'count': 1, 'high': 5, 'low': 4}, histogram['buckets'])
+
+  # Verify that when Chrome receives a non-4xx response through a Data Reduction
+  # Proxy that doesn't set a proper via header, Chrome falls back to the next
+  # available proxy.
+  def testMissingViaHeaderNon4xxFallback(self):

[megjablon, 2017/03/11 00:51:47]

The telemetry tests check the remote port, should we be doing that somewhere in
here?

[sclittle, 2017/03/11 01:29:03]

Done.

+    with TestDriver() as test_driver:
+      test_driver.AddChromeArg('--enable-spdy-proxy-auth')
+
+      # Set the primary Data Reduction Proxy to be the test server, which does
+      # not add any Via headers. The fallback Data Reduction Proxy is set to the
+      # canonical Data Reduction Proxy target.
+      test_driver.AddChromeArg('--data-reduction-proxy-http-proxies='
+                               'http://chromeproxy-test.appspot.com;'
+                               'http://compress.googlezip.net')
+
+      # Load a page that should fall back off of the test server proxy, and onto
+      # the canonical proxy that will set the correct Via header.
+      test_driver.LoadURL('http://chromeproxy-test.appspot.com/default')
+      responses = test_driver.GetHTTPResponses()
+      self.assertNotEqual(0, len(responses))
+      for response in responses:
+        self.assertHasChromeProxyViaHeader(response)
+
+      # Check that the BypassTypePrimary histogram has a single entry in the
+      # MissingViaHeaderOther category (which is enum value 5), to make sure
+      # that the bypass was caused by the missing via header logic and not
+      # something else.
+      histogram = test_driver.GetHistogram(
+          "DataReductionProxy.BypassTypePrimary")
+      self.assertEqual(1, histogram['count'])
+      self.assertIn({'count': 1, 'high': 6, 'low': 5}, histogram['buckets'])
 
 if __name__ == '__main__':
   IntegrationTest.RunAllTests()