[Merge] lp:~osomon/webbrowser-app/uriboni-tab-context-menu into lp:webbrowser-app

[Olivier Tilloy]

Note to the reviewer: this is based on and supersedes a previous proposal by Ugo, see initial review at https://code.launchpad.net/~uriboni/webbrowser-app/tab-context-menu/+merge/268220.
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https://code.launchpad.net/~osomon/webbrowser-app/uriboni-tab-context-menu/+merge/272148
Your team Ubuntu Phablet Team is requested to review the proposed merge of lp:~osomon/webbrowser-app/uriboni-tab-context-menu into lp:webbrowser-app.