Add Histogram functionality.

tools/chrome_proxy/webdriver/simple_smoke.py

Index: tools/chrome_proxy/webdriver/simple_smoke.py
diff --git a/tools/chrome_proxy/webdriver/simple_smoke.py b/tools/chrome_proxy/webdriver/simple_smoke.py
index f70cbbb8a15c6a50f51705616cbb71d3a10154ef..5513be9e05d6f55349456611b55fe1b8e64f3069 100644
--- a/tools/chrome_proxy/webdriver/simple_smoke.py
+++ b/tools/chrome_proxy/webdriver/simple_smoke.py
@@ -13,7 +13,7 @@ class SimpleSmoke(IntegrationTest):
   # Simple example integration test.
   def TestCheckPageWithProxy(self):
     with TestDriver() as t:
-      t.AddChromeArgs(['--enable-spdy-proxy-auth'])
+      t.AddChromeArg('--enable-spdy-proxy-auth')
       t.SetURL('http://check.googlezip.net/test.html')
       t.LoadPage()
       print 'Document Title: ', t.ExecuteJavascriptStatement('document.title',
@@ -24,6 +24,15 @@ class SimpleSmoke(IntegrationTest):
         print "URL: %s, ViaHeader: %s, XHR: %s" % (response.url,
           response.ResponseHasViaHeader(), response.WasXHR())
 
+  # Show how to get a histogram.
+  def TestPingbackHistogram(self):
+    with TestDriver() as t:
+      t.AddChromeArg('--enable-spdy-proxy-auth')
+      t.SetURL('http://check.googlezip.net/test.html')
+      t.LoadPage()
+      t.LoadPage()
+      print t.GetHistogram('DataReductionProxy.Pingback.Attempted')
+
 if __name__ == '__main__':
   test = SimpleSmoke()
   test.RunAllTests()