addView(view, size, index = this.viewItems.length, skipLayout) {
        this.doAddView(view, size, index, skipLayout);
    }
Add a {@link IView view} to this {@link SplitView}.

@param view The view to add.
@param size Either a fixed size, or a dynamic {@link Sizing} strategy.
@param index The index to insert the view on.
@param skipLayout Whether layout should be skipped.