get_device_browser: Fix browser string for mobile.

Now get_device_browser() returns 'Zulip' for 'ZulipAndroid' and
'ZulipMobile'.

zerver/signals.py

@@ -27,6 +27,8 @@ def get_device_browser(user_agent):
         return "Internet Explorer"
     elif "edge" in user_agent:
         return "Edge"
+    elif "zulip" in user_agent:
+        return "Zulip"
     else:
         return None
 

zerver/tests/test_new_users.py

@@ -87,6 +87,8 @@ class TestBrowserAndOsUserAgentStrings(ZulipTestCase):
             ('Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) ' +
                 'AppleWebKit/602.3.12 (KHTML, like Gecko) ' +
                 'Version/10.0.2 Safari/602.3.12', 'Safari', 'MacOS'),
+            ('ZulipAndroid/1.0', 'Zulip', 'Android'),
+            ('ZulipMobile/1.0', 'Zulip', None),
             ('', None, None),
         ]