To be implemented by @mozilla.org/dom/activities/ui-glue;1
This method is called even if the size of {@code activities} is 0 so that the callee can
decide whether or not to defer the request to an alternate activity system.
| options | The ActivityOptions object in the form of { name: "send", data: { ... } } |
| activities | A json blob which is an array of { "title":"...", "icon":"..." }. |
| callback | The callback to send the index of the choosen activity, or the result. |