Add vendored template for Browser Performance

Provides basic job definition for running sitespeed.io
performance test.

We also provided the users a way to override sitespeed
options through job variables.

ee/changelogs/unreleased/eb-browser-performance-vendored-template.yml

+---
+title: Add vendored template for Browser Performance Testing
+merge_request: 17319
+author:
+type: added

ee/lib/ee/gitlab/template/gitlab_ci_yml_template.rb

@@ -18,7 +18,8 @@ module EE
 
           def categories_ee
             {
-              'Security' => 'Security'
+              'Security' => 'Security',
+              'Verify' => 'Verify'
             }
           end
         end

ee/spec/lib/ee/gitlab/template/gitlab_ci_yml_template_spec.rb

@@ -3,17 +3,19 @@
 require 'spec_helper'
 
 describe Gitlab::Template::GitlabCiYmlTemplate do
-  subject { described_class }
-
   describe '.all' do
+    let(:templates) { described_class.all.map(&:name) }
+
     it 'finds the Security Products templates' do
-      all = subject.all.map(&:name)
+      expect(templates).to include('Container-Scanning')
+      expect(templates).to include('DAST')
+      expect(templates).to include('Dependency-Scanning')
+      expect(templates).to include('License-Management')
+      expect(templates).to include('SAST')
+    end
 
-      expect(all).to include('Container-Scanning')
-      expect(all).to include('DAST')
-      expect(all).to include('Dependency-Scanning')
-      expect(all).to include('License-Management')
-      expect(all).to include('SAST')
+    it 'finds the Verify templates' do
+      expect(templates).to include('Browser-Performance')
     end
   end
 end

lib/gitlab/ci/templates/Browser-Performance.gitlab-ci.yml

+# Read more about the feature here: https://docs.gitlab.com/ee/user/project/merge_requests/browser_performance_testing.html
+
+stages:
+  - build
+  - test
+  - deploy
+  - performance
+
+performance:
+  stage: performance
+  image: docker:git
+  variables:
+    URL: https://example.com
+    SITESPEED_VERSION: 6.3.1
+    SITESPEED_OPTIONS: ''
+  services:
+    - docker:stable-dind
+  script:
+    - mkdir gitlab-exporter
+    - wget -O ./gitlab-exporter/index.js https://gitlab.com/gitlab-org/gl-performance/raw/master/index.js
+    - mkdir sitespeed-results
+    - docker run --shm-size=1g --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io:$SITESPEED_VERSION --plugins.add ./gitlab-exporter --outputFolder sitespeed-results $URL $SITESPEED_OPTIONS
+    - mv sitespeed-results/data/performance.json performance.json
+  artifacts:
+    paths:
+      - sitespeed-results/
+    reports:
+      performance: performance.json