js/libs/ember-1.5.1.js
function(view, childView, options) {
    var buffer = view.buffer, _childViews = view._childViews;

    childView = view.createChildView(childView, options);
    if (!_childViews.length) { _childViews = view._childViews = _childViews.slice(); }
    _childViews.push(childView);

    childView.renderToBuffer(buffer);

    view.propertyDidChange('childViews');

    return childView;
  }
function(view, childView, options) {
    var buffer = view.buffer, _childViews = view._childViews;

    childView = view.createChildView(childView, options);
    if (!_childViews.length) { _childViews = view._childViews = _childViews.slice(); }
    _childViews.push(childView);

    childView.renderToBuffer(buffer);

    view.propertyDidChange('childViews');

    return childView;
  }
when a view is rendered in a buffer, appending a child view will render that view and append the resulting buffer into its buffer.