Merge branch '11989-track-clicks-on-sign_in-with-snowplow' into 'master'

Add trackEvent when accessing the Register tab

See merge request gitlab-org/gitlab-ce!29336

app/views/devise/shared/_tabs_normal.html.haml

@@ -3,4 +3,4 @@
     %a.nav-link.qa-sign-in-tab.active{ href: '#login-pane', data: { toggle: 'tab' }, role: 'tab' } Sign in
   - if allow_signup?
     %li.nav-item{ role: 'presentation' }
-      %a.nav-link.qa-register-tab{ href: '#register-pane', data: { toggle: 'tab' }, role: 'tab' } Register
+      %a.nav-link.qa-register-tab{ href: '#register-pane', data: { track_label: 'sign_in_register', track_property: 'sign_in', track_event: 'click_button', track_value: 'register', toggle: 'tab' }, role: 'tab' } Register