Bug 741047 - Implement opening in-content preferences to a given view. r=Gijs

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extra : rebase_source : cf486a6e5c8673d66a57e3b726b58073c694a338
Bug 738797 - Enable the in-content preferences by default. r=Unfocused

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extra : rebase_source : 4c06ec299a082f4a2c587fe5cbeff3b0e5b21548