`ApplicationController#add_gon_variables` Job Failed #303239823 (breaks in CE)

This test breaks when run in CE:

IS_GITLAB_EE=0 bundle exec rspec spec/controllers/application_controller_spec.rb:75

Failure details

Job #303239823 failed for 7bb7a8d5:

Note, although this is a master:broken for gitlab-foss, the change has to happen in gitlab for it to be merged to gitlab-foss so this issue is in gitlab.

2) ApplicationController#add_gon_variables with json format behaves like setting gon variables sets gon variables
     Failure/Error: expect(json_response.size).not_to be_zero
       expected `0.zero?` to return false, got true
     Shared Example Group: "setting gon variables" called from ./spec/controllers/application_controller_spec.rb:113
     # ./vendor/ruby/2.6.0/gems/rspec-support-3.8.2/lib/rspec/support.rb:97:in `block in <module:Support>'
     # ./vendor/ruby/2.6.0/gems/rspec-support-3.8.2/lib/rspec/support.rb:106:in `notify_failure'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/fail_with.rb:35:in `fail_with'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/handler.rb:40:in `handle_failure'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/handler.rb:72:in `block in handle_matcher'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/handler.rb:27:in `with_matcher'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/handler.rb:70:in `handle_matcher'
     # ./vendor/ruby/2.6.0/gems/rspec-expectations-3.8.4/lib/rspec/expectations/expectation_target.rb:78:in `not_to'
     # ./spec/controllers/application_controller_spec.rb:75:in `block (4 levels) in <top (required)>'