Allow screen URL pattern to be changed.

lib/units/device/plugins/screen.js

@@ -6,6 +6,7 @@ var Promise = require('bluebird')
 var syrup = require('stf-syrup')
 var httpProxy = require('http-proxy')
 var adbkit = require('adbkit')
+var _ = require('lodash')
 
 var logger = require('../../../util/logger')
 var lifecycle = require('../../../util/lifecycle')
@@ -32,11 +33,12 @@ module.exports = syrup.serial()
     )
 
     plugin.publicPort = options.ports.pop()
-    plugin.publicUrl = util.format(
-      'ws://%s:%s'
-    , options.publicIp
-    , plugin.publicPort
-    )
+    plugin.publicUrl = _.template(options.screenWsUrlPattern, {
+      publicIp: options.publicIp
+    , publicPort: plugin.publicPort
+    , privatePort: plugin.privatePort
+    , serial: options.serial
+    })
 
     function run(cmd) {
       return adb.shell(options.serial, util.format(
@@ -165,7 +167,11 @@ module.exports = syrup.serial()
 
     return startService()
       .then(forwardService)
-      .then(startProxy)
+      .then(function() {
+        if (!options.disableScreenPublicProxy) {
+          return startProxy()
+        }
+      })
       .then(function() {
         plugin.info = function(id) {
           return run(util.format('-d %d -i', id))