handleBackspaceKey method

@override void handleBackspaceKey(KeyboardEvent event)

Return focus to the textbox and delete a character.

WAI-ARIA Guidelines: https://www.w3.org/TR/wai-aria-practices/#combobox

Implementation

@override
void handleBackspaceKey(html.KeyboardEvent event) {
  if (activeModel.activeItem != null) {
    activeModel.activate(null);
  }
}