bug 904104 fix window.close usage from chat and social panels, r=felipc
Bug 896281 - Part 1: Disable synced tab for guest session. r=sriram

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extra : rebase_source : 621253f2a28aca48fff7957c20fde7f8097887a2
Bug 896281 - Part 2: Remove Sync pref for guest session. r=wesj

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extra : rebase_source : 9936a08abc8c639d2cb57a65f9c964e9c6e8568b