adb push user.js /system/b2g/defaults/pref
adb shell sync && adb reboot
* this overrides the User Agent string to Android
adb root
adb pull /system/b2g/defaults/pref/user.js .
echo 'pref("general.useragent.override", "Mozilla/5.0 (Linux; U; Android 4.3.0; en-us; LG-D30008M Build/1.1FFxOS) AppleWebkit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30");' >> user.js
adb remount
adb push user.js /system/b2g/defaults/pref
adb shell sync && adb reboot
* This adds the pref to disable dns prefetching : {{bug|856530}}