From bug 595848 comment 14: My thinking is that rather than being an API on AddonManager or AddonManagerPrivate it'd probably be an API in the extensions UI itself. When the UI opens a notification would go out saying so and giving consumers a chance to register themselves and then we'd create the category selector and call the category object whenever it was viewed. We'd just leave it up to the category provider to add whatever UI it wanted in its own way.

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