Simplify GPUSink constructors by just passing the config object

Also, remove the never-used gpu_threading flag. In limited
testing, it makes things slower.

Change-Id: I40ae0c8e5b79992c90845035a06536ed9d6626b5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/240202
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed