handleKeyEvent_(evt) {
    if (this.isLocked_) {
      return;
    }

    switch (evt.keyCode) {
      case goog.events.KeyCodes.BACKSPACE:
        this.removeChipOnBackspace_();
        break;
      default:
        if (goog.events.KeyCodes.isCharacterKey(evt.keyCode)) {
          this.increaseInputArea_();
        }
    }
  }
Handles keyboard events. Ignores them if ChipHolder is locked.
@param {goog.events.KeyEvent} evt The keyboard event to handle.
@private