[Merge] lp:~fboucault/webbrowser-app/workaround_new_tab_never_unloaded into lp:webbrowser-app/staging

[Olivier Tilloy]

Review: Needs Fixing

This breaks webbrowser_app.tests.test_new_tab_view.TestNewTabViewLifetime.test_new_tab_view_is_shared_between_tabs
-- 
https://code.launchpad.net/~fboucault/webbrowser-app/workaround_new_tab_never_unloaded/+merge/317113
Your team Ubuntu Phablet Team is subscribed to branch lp:webbrowser-app/staging.