The IRawChildrenContainer interface defines the APIs for containers that
can return an IChildList that represents all their children.
This interface should be implemented by any container that has overridden
IChildList APIs such as numChildren and addChild()
method to manage only a subset of its actual children.
The mx.core.Container class, for example, has a set of content children
separate from the non-content children, such as borders, title bars,