_handleCustomSize() {
      switch (this.size) {
        case _IllustrationMessageSize.default.Base:
          this.media = IllustratedMessage_1.MEDIA.BASE;
          return;
        case _IllustrationMessageSize.default.Spot:
          this.media = IllustratedMessage_1.MEDIA.SPOT;
          return;
        case _IllustrationMessageSize.default.Dialog:
          this.media = IllustratedMessage_1.MEDIA.DIALOG;
          return;
        default:
          this.media = IllustratedMessage_1.MEDIA.SCENE;
      }
    }
Modifies the IM styles in accordance to the `size` property's value.
Note: The resize handler has no effect when size is different than "Auto".
@private
@since 1.5.0