Bug 1338260. Add Fennec-only UA override for directv.com. r=mconnor

They use an older version of Sencha Touch (v2.1.0) which is known
to not be compatibile with Firefox. However, pretending to be Chrome
fixes the issue of not being able to scroll and various paint bugs.

MozReview-Commit-ID: K35ll42Xxlt

--HG--
extra : rebase_source : 26f2e68ff2bc6be7d00a3eba1bedd56a9a7d62be

mobile/android/app/ua-update.json.in

@@ -9,5 +9,7 @@
   // bug 1177298, www.nhk.or.jp
   "nhk.or.jp": "\\)\\s# AppleWebKit ",
   // bug 1177298, uniqlo.com
-  "uniqlo.com": "\\)\\s#) Mobile Safari "
+  "uniqlo.com": "\\)\\s#) Mobile Safari ",
+  // bug 1338260, directv.com
+  "directv.com": "Mozilla/5.0 (Linux; Android 6.0.1; SM-G920F Build/MMB29K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.91 Mobile Safari/537.36"
 }