PDFDocumentImage has an optimization to use a cached bitmap if we're doing low-quality interpolation, which was intended to only occur during a live resize and when we were guaranteed to get a high-quality paint shortly afterwards. However, on iOS there are some scenarios where we *always* use low-quality interpolation, and there are also CSS properties that allow content to specify that it always wants low-quality interpolation. This results in caching the PDF at the initial scale it's rendered at, and never re-rendering. We should only do this optimization if we're actually in a live resize, and will eventually get a high-quality paint.
Created attachment 237723 [details] crazy WIP patch
<rdar://problem/18252268>