[graphite] Track image size uniforms separately from proxies

This makes it easier to decide whether to use hardware tiling when we
don't have an actual proxy, for example when precompiling shaders.

Bug: b/238754663
Change-Id: Iff908653005b37d50cb0c3b94b15cdd321cf36a1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/765356
Commit-Queue: James Godfrey-Kittle <jamesgk@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
6 files changed