feat(webdriver): allow configuration of all SeleniumServer arguments

You can now pass a complete object of configuration for the SeleniumServer class.
This allows enabling loopback on the selenium server.

docs/referenceConf.js

@@ -38,6 +38,10 @@ exports.config = {
   // seleniumArgs: ['-browserTimeout=60']
   // Ignored if seleniumServerJar is null.
   seleniumArgs: [],
+  // Can be an object which will be passed to the SeleniumServer class as args.
+  // If you specify `args` or `port` in this object, it will overwrite the values
+  // set via `seleniumPort` and `seleniumArgs`.
+  localSeleniumStandaloneOpts: null,
   // ChromeDriver location is used to help find the chromedriver binary.
   // This will be passed to the Selenium jar as the system property
   // webdriver.chrome.driver. If null, Selenium will

lib/driverProviders/local.js

@@ -72,15 +72,24 @@ LocalDriverProvider.prototype.setupEnv = function() {
 
   log.puts('Starting selenium standalone server...');
 
+  var serverConf = this.config_.localSeleniumStandaloneOpts || {};
+
+  // If args or port is not set use seleniumArgs and seleniumPort
+  // for backward compatibility
+  if (serverConf.args === undefined) {
+    serverConf.args = this.config_.seleniumArgs || [];
+  }
+  if (serverConf.port === undefined) {
+    serverConf.port = this.config_.seleniumPort;
+  }
+
   // configure server
   if (this.config_.chromeDriver) {
-    this.config_.seleniumArgs.push('-Dwebdriver.chrome.driver=' +
+    serverConf.args.push('-Dwebdriver.chrome.driver=' +
       this.config_.chromeDriver);
   }
-  this.server_ = new remote.SeleniumServer(this.config_.seleniumServerJar, {
-      args: this.config_.seleniumArgs,
-      port: this.config_.seleniumPort
-    });
+
+  this.server_ = new remote.SeleniumServer(this.config_.seleniumServerJar, serverConf);
 
   //start local server, grab hosted address, and resolve promise
   this.server_.start().then(function(url) {