Reland "Refactor stencil clip mask generation into helper"

This reverts commit de228e53fee75fa8711beed5b7dfbe8900f424cb.

Reason for revert: GrReducedClip now assumes context isn't abandoned,
windowrectangles GM abuses GrReducedClip and has to be abandon-aware.

Original change's description:
> Revert "Refactor stencil clip mask generation into helper"
>
> This reverts commit 8b3a8a5238f5be31c4408c212d867f4765e3e29a.
>
> Reason for revert: GM assert failure
>
> Original change's description:
> > Refactor stencil clip mask generation into helper
> >
> > Change-Id: If3dc80efde3b44e87ba8e7af3a258896ec5e78e6
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/288977
> > Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> > Reviewed-by: Chris Dalton <csmartdalton@google.com>
> > Reviewed-by: Brian Salomon <bsalomon@google.com>
>
> TBR=bsalomon@google.com,csmartdalton@google.com,michaelludwig@google.com
>
> Change-Id: I16559f791601145f57d147cdae345c200af313f1
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289237
> Reviewed-by: Michael Ludwig <michaelludwig@google.com>
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>

# Not skipping CQ checks because this is a reland.

Change-Id: I6a9372edecd0bdc1a38464ab85f7b7f3ca85e5ed
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/289239
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
9 files changed