Use case

Once flutter/engine#53201 lands, the CanvasKit backend will use <img> tags to decode images in many cases. However, we cannot use <img> to decode animated images and get single frames out, so we must use Skia to decode those images. However, we don't actually determine if the images are animated before defaulting to Skia decoding, we conservatively assume all GIF and WebP images are animated.

Proposal

Determine if the image is actually animated by reading the headers and determining that way. Only use Skia to decode if the image is actually animated, otherwise use <img>.