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

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extra : rebase_source : 9b9c58a967bb52b596457f41b697085c46fb0ba6
Bug 738797 - Enable the in-content preferences by default. r=Unfocused

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extra : rebase_source : bcff4e914e2b66da1b7a5b93ef21dc153519b6e4