This view contains the iOS keyboard. It is made up of the background (UIKBInputBackdropView) and the foreground (UIKeyboardAutomatic)
recursiveDefinition example on 7.1.2:
<UIPeripheralHostView: frame = (0 568; 320 252);>
| <UIKBInputBackdropView: frame = (0 0; 320 252);>
| | <UIKBBackdropView: frame = (0 0; 320 252);>
| | | <_UIBackdropEffectView: frame = (0 0; 320 252);>
| <UIKeyboardAutomatic: frame = (0 0; 320 252);>