### Requirements

[taras-bl]

Requirements

• Filling out the template is required. Any pull request that does not include enough information to be reviewed in a timely manner may be closed at the maintainers' discretion.
• All new code requires tests to ensure against regressions

Description of the Change

This allows focus to be transferred to the containing pane when right clicking on a tab. Helpful for atom/tree-view#1205 where if the Tree View was focused and someone tried renaming a tab by right clicking on it, the resulting dialog would be for the focused Tree View entry rather than the tab.

Also:

• Remove unused right-clicked class. I plan to remove rightClickedItem later as well.
• Switch from the non-standard event.which to event.button.

Alternate Designs

None.

Benefits

Focus will be transferred correctly.

Possible Drawbacks

I foresee none.

Applicable Issues

Refs atom/tree-view#1205
Refs atom/atom#16192
Refs atom/atom#21616

Originally posted by @winstliu in atom/tabs#531