Keyboard UI interacts with unfocused controls when displaying a modal dialog

[handsome-b-wonderful]

What happens?

When displaying a modal dialog (example "Save Changes") the main UI is blurred and the user presented with a subset of options (in this case several buttons). Using the keyboard (example: TAB) iteracts with the unfocused controls in the UI. The controls of the modal dialog are not interactive with the keyboard (beyond enter/return which in this example is SAVE)

What's expected?

Keyboard interaction is supported and restricted to the controls of the focused UI. Example repeatedly pressing TAB cycles only the buttons displayed in the dialog. The unfocused UI is not interactive.

Steps to reproduce

1. create a new note and make some changes
2. press ESCAPE to display the "Save Changes" dialog
3. press TAB a few times or edit a text control

You will see the blurred controls receiving focus and they are interactive. In addition content can be edited.