[Merge] lp:~abreu-alexandre/webbrowser-app/remove-session-storage into lp:webbrowser-app

[Olivier Tilloy]

I verified that running the AP tests on krillin #44 without the changes from this MR works reliably without crashes, so the crash seems to be a regression introduced by this MR.
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https://code.launchpad.net/~abreu-alexandre/webbrowser-app/remove-session-storage/+merge/234144
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