Always allow the performance bar to be enabled for admins

lib/gitlab/performance_bar.rb

@@ -5,6 +5,7 @@ module Gitlab
 
     def self.enabled?(user = nil)
       return true if Rails.env.development?
+      return true if user&.admin?
       return false unless user && allowed_group_id
 
       allowed_user_ids.include?(user.id)

spec/lib/gitlab/performance_bar_spec.rb

@@ -25,6 +25,12 @@ describe Gitlab::PerformanceBar do
       expect(described_class.enabled?(nil)).to be_falsy
     end
 
+    it 'returns true when given user is an admin' do
+      user = build_stubbed(:user, :admin)
+
+      expect(described_class.enabled?(user)).to be_truthy
+    end
+
     it 'returns false when allowed_group_id is nil' do
       expect(described_class).to receive(:allowed_group_id).and_return(nil)