Add option to use the same Chrome profile

If CHROME_REUSE_PROFILE is enabled, QA will use the same profile
everytime, which will be useful for local QA runs as the browser can
then cache assets, etc.

qa/qa/runtime/browser.rb

@@ -70,6 +70,13 @@ module QA
             options.add_argument("disable-gpu")
           end
 
+          # Use the same profile on QA runs if CHROME_REUSE_PROFILE is true.
+          # Useful to speed up local QA.
+          if QA::Runtime::Env.reuse_chrome_profile?
+            qa_profile_dir = ::File.expand_path('../../tmp/qa-profile', __dir__)
+            options.add_argument("user-data-dir=#{qa_profile_dir}")
+          end
+
           # Disable /dev/shm use in CI. See https://gitlab.com/gitlab-org/gitlab-ee/issues/4252
           options.add_argument("disable-dev-shm-usage") if QA::Runtime::Env.running_in_ci?
 

qa/qa/runtime/env.rb

@@ -30,6 +30,11 @@ module QA
         enabled?(ENV['CHROME_HEADLESS'])
       end
 
+      # set to 'true' to have Chrome use a fixed profile directory
+      def reuse_chrome_profile?
+        enabled?(ENV['CHROME_REUSE_PROFILE'], default: false)
+      end
+
       def accept_insecure_certs?
         enabled?(ENV['ACCEPT_INSECURE_CERTS'])
       end