[Merge] lp:~ahayzen/webbrowser-app/fix-1638337-progress-bar-shown-new-tab into lp:webbrowser-app/staging

[Olivier Tilloy]

Could you please add an autopilot test for that regression?
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https://code.launchpad.net/~ahayzen/webbrowser-app/fix-1638337-progress-bar-shown-new-tab/+merge/309838
Your team Ubuntu Phablet Team is requested to review the proposed merge of lp:~ahayzen/webbrowser-app/fix-1638337-progress-bar-shown-new-tab into lp:webbrowser-app/staging.