Provides support for MovieClip animations (or a single frame Sprite) when this class is overridden.
For example, the OpenFL SWF library provides a Timeline generated from SWF assets. However, any editor that may provide UI or display elements could be used to generate assets for OpenFL timelines.
To implement a custom Timeline, please override this class. Each Timeline can set their original animation frame rate, and can also provide Scenes or FrameScripts. OpenFL will automatically execute FrameScripts and request frame updates.
There are currently three internal methods which should not be called by the user, which can be overridden to implement a new type of Timeline:
attachMovieClip(); enterFrame(); initializeSprite();