Using @custom-browser Cucumber tag instead of @user_agent

Implementing the convention:
https://www.mediawiki.org/wiki/Manual:Coding_conventions/Selenium#Option
al_tags

Bug: 61458
Change-Id: Iac411401a08eadfb04fd43f1d93ce2fd36fbea4a

tests/browser/Gemfile.lock

@@ -4,13 +4,13 @@ GEM
     builder (3.2.2)
     childprocess (0.5.1)
       ffi (~> 1.0, >= 1.0.11)
-    cucumber (1.3.10)
+    cucumber (1.3.11)
       builder (>= 2.1.2)
       diff-lcs (>= 1.1.3)
       gherkin (~> 2.12)
       multi_json (>= 1.7.5, < 2.0)
       multi_test (>= 0.0.2)
-    data_magic (0.17)
+    data_magic (0.18)
       faker (>= 1.1.2)
       yml_reader (>= 0.2)
     diff-lcs (1.2.5)
@@ -22,7 +22,7 @@ GEM
     headless (1.0.1)
     i18n (0.6.9)
     json (1.8.1)
-    mediawiki_selenium (0.2.7)
+    mediawiki_selenium (0.2.8)
       cucumber (~> 1.3, >= 1.3.10)
       headless (~> 1.0, >= 1.0.1)
       json (~> 1.8, >= 1.8.1)
@@ -32,13 +32,13 @@ GEM
       rspec-expectations (~> 2.14, >= 2.14.4)
       syntax (~> 1.2, >= 1.2.0)
     mime-types (2.1)
-    multi_json (1.8.4)
+    multi_json (1.9.0)
     multi_test (0.0.3)
     net-http-persistent (2.9.4)
-    page-object (0.9.6)
+    page-object (0.9.7)
       page_navigation (>= 0.9)
-      selenium-webdriver (>= 2.39.0)
-      watir-webdriver (>= 0.6.7)
+      selenium-webdriver (>= 2.40.0)
+      watir-webdriver (>= 0.6.8)
     page_navigation (0.9)
       data_magic (>= 0.14)
     rest-client (1.6.7)

tests/browser/features/accept_language.feature

@@ -1,4 +1,4 @@
-@language @phantomjs-bug @sandbox.translatewiki.net
+@custom-browser @phantomjs-bug @sandbox.translatewiki.net
 Feature: Accept-Language
 
   Scenario Outline: Accept-Language

tests/browser/features/support/env.rb

@@ -1,2 +1 @@
-require_relative "hooks"
 require "mediawiki_selenium"

tests/browser/features/support/hooks.rb

@@ -1,4 +0,0 @@
-Before("@language") do |scenario|
-  @language = true
-  @scenario = scenario
-end

tests/browser/tags.txt

@@ -4,7 +4,7 @@ This file contains the descriptions of the tags we use.
 @commons.wikimedia.beta.wmflabs.org
   Test is run on this domain unless further excluded by other tags.
 
-@language
+@custom-browser
   This tests needs support from Accept-Language header setting from the
   webdriver.