GrClips provided as pointers to GrRTC

A null clip represents no high-level clipping is necessary (the implicit
clip to the render target's logical dimensions is fine).

This also removes GrNoClip and GrFixedClip::Disabled() since they are
replaced with just nullptr.

By allowing nullptr to represent no intended clipping, it makes it easier
to require GrClip and GrAppliedClip objects to know about the dimensions
of the device. If we required a non-null clip object to represent no
clipping, we'd have to have an instance for each device based on its
size and that just became cumbersome.

Bug: skia:10205
Change-Id: Ie30cc71820b92d99356d393a4c98c8677082e761
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/290539
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
79 files changed