Add video via header check

tools/chrome_proxy/webdriver/video.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 Video(IntegrationTest):
+
+  # Check videos are proxied.
+  def testCheckVideoHasViaHeader(self):
+    with TestDriver() as t:
+      t.AddChromeArg('--enable-spdy-proxy-auth')
+      t.LoadURL(
+        'http://check.googlezip.net/cacheable/video/buck_bunny_tiny.html')
+      for response in t.GetHTTPResponses():
+        self.assertHasChromeProxyViaHeader(response)
+
+if __name__ == '__main__':
+  IntegrationTest.RunAllTests()