A policy for discarding tile images that match a known image containing a "missing" image.
Object with the following properties:
Determines if the discard policy is ready to process images.
True if the discard policy is ready to process images; otherwise, false.
Given a tile image, decide whether to discard that image.
||HTMLImageElement||An image to test.|
True if the image should be discarded; otherwise, false.
shouldDiscardImagemust not be called before the discard policy is ready.