and pageActions.
Before this change, browserActions and pageActions did not trigger
onClick events when middle-clicked, and no information on the button or
any modifiers were passed in the onClick event. With this change, middle
clicking triggers an event, and a clickData object is passed in the
onClick event, with the button and a list of modifiers.
Differential Revision: https://phabricator.services.mozilla.com/D41492
24a36c3701