Tiling pattern cache may incorrectly cache patterns with same name

[brendandahl]

It's possible for a PDF page to have multiple resource dictionaries which could have patterns (shading or tiling) that have the same names. Our cache currently works off of name, so we could potentially be caching one pattern and retrieving the wrong one if the name is the same, but the resource dictionary has changed.

I'm not aware of any PDFs affected by this issue, but issue6737.pdf has an example of this with radial shadings. There are two patterns P1 and P2 which each have their own resource dictionaries. Each of those resource dictionaries has a pattern named Sh0, but they are different shadings.