メモ：DisplayObject subclass

ちょいとメモ。
Loader.content（もしくはLoaderInfo.content）の抽出に悪戦苦闘。
cloneの必要があるのかと思ったがどうもそーでもないっぽい。BitmapDataではなくBitmapらしい。そもそもLoader自体がDisplayObjectのサブクラスだから、そゆことをしてはいけないのかもしれない。

Shape for a “canvas” for drawing content on-screen. In particular, if you want to create an instance for drawing shapes on the screen, and it won't be a container for other display objects, you'll gain significant performance benefits using Shape instead of Sprite or MovieClip.
A loaded image will be a Bitmap instance.
A loaded SWF file written in ActionScript 3.0 will be a Sprite or MovieClip instance (or an instance of a subclass of those classes, as specified by the content creator).
Sprite if the object will be created using only ActionScript, or as the base class for a custom display object that will be created and manipulated solely with ActionScript.
If you are creating a class that will be associated with a movie clip symbol in the Flash library, choose one of these DisplayObjectContainer subclasses as your class's base class:
* MovieClip if the associated movie clip symbol has content on more than one frame
* Sprite if the associated movie clip symbol has content only on the first frame

話はずれるが、
http://livedocs.adobe.com/flash/9.0/ActionScriptLangRefV3/
と
http://livedocs.adobe.com/flash/9.0/main/wwhelp/wwhimpl/js/html/wwhelp.htm
って一つにまとまらないのかしら？
タブブラウザだと切り替えがめんどくさい。（ウインドウ一つ追加すればいいだけなんだけど）