Update GrTextureOp to use index buffer offsets for draws

This should, hopefully, be faster on GL as we will only need to update the index-range for a draw rather than the offset into an vertex buffer.

Change-Id: I09e54c37262168661443fa8bf8d3b43cd8faa9db
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/251757
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
4 files changed