Use dstColorSpace in SkPictureShader cache key

Starting with the bug fix + test.

Broken off of:
https://skia-review.googlesource.com/c/13976

Bug: skia:
Change-Id: If6c28e2dfb0c5340c48e943d0313a9ea9515a6c3
Reviewed-on: https://skia-review.googlesource.com/14061
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Matt Sarett <msarett@google.com>
3 files changed