More SkISizification in GPU code.

Uses SkISize instead of separate width/height variables in many places.

No functional change.

Change-Id: If87b2c57e43d810f0820c4e3c9ef8e6b8ebd10ba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/249886
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
79 files changed