Use devtools to set user agent in chromedriver

chrome/test/chromedriver/test/run_py_tests.py

Index: chrome/test/chromedriver/test/run_py_tests.py
diff --git a/chrome/test/chromedriver/test/run_py_tests.py b/chrome/test/chromedriver/test/run_py_tests.py
index 2c5e728952ef44f8938b54e24d74f51f13a94c72..72fa647ac1e0644e6ad58b49e6a0f27119babbd4 100755
--- a/chrome/test/chromedriver/test/run_py_tests.py
+++ b/chrome/test/chromedriver/test/run_py_tests.py
@@ -1836,7 +1836,7 @@ class ChromeLogPathCapabilityTest(ChromeDriverBaseTest):
     self.assertTrue(self.LOG_MESSAGE in open(tmp_log_path.name).read())
 
 
-class MobileEmulationCapabilityTest(ChromeDriverBaseTest):
+class MobileEmulationCapabilityTest(ChromeDriverBaseTestWithWebServer):
   """Tests that ChromeDriver processes chromeOptions.mobileEmulation.
 
   Makes sure the device metrics are overridden in DevTools and user agent is
@@ -1905,6 +1905,24 @@ class MobileEmulationCapabilityTest(ChromeDriverBaseTest):
     body_tag = driver.FindElement('tag name', 'body')
     self.assertEqual("Agent Smith", body_tag.GetText())
 
+  def testUserAgentNewTab(self):
+    driver = self.CreateDriver(
+        mobile_emulation = {'userAgent': 'Agent Smith'})
+    driver.Load(self.GetHttpUrlForFile('/chromedriver/empty.html'))
+    old_windows = driver.GetWindowHandles()
+    user_agent_url = self._http_server.GetUrl() + '/userAgent'
+    driver.ExecuteScript(
+      ('document.body.innerHTML = "<a href=\\"%s\\" '
+       'target=\\"_blank\\">test</a>";') % user_agent_url)
+
+    link = driver.FindElement('tag name', 'a')
+    driver.MouseMoveTo(link)
+    driver.MouseClick()
+    new_window = self.WaitForNewWindow(driver, old_windows)
+    driver.SwitchToWindow(new_window)
+    body_tag = driver.FindElement('tag name', 'body')
+    self.assertEqual("Agent Smith", body_tag.GetText())
+
   def testDeviceName(self):
     driver = self.CreateDriver(
         mobile_emulation = {'deviceName': 'Google Nexus 5'})