Comment 53 for bug 306017

Created attachment 625243
WIP v6: frontend: Rework the window.open() case so it won't recur.

The window.open() case could recur in the previous iteration, so this prevents that by ensuring it only happens if the data hasn't been set yet.

The backend patch removes the notion of a current engine from the search service, and the frontend also updates the observers to not look for the current engine change topic.

The tests are also updated to handle the search service API with the current engine removed.

When adding an engine that's set to be used immediately, only the active window's active tab has the engine changed.