Revert "Delete GPU alpha clip masks"

This reverts commit a466228a616b1b02ede2d4389fefcfc839a54a25.

Reason for revert: Turned up a vulkan driver bug

Original change's description:
> Delete GPU alpha clip masks
> 
> The cost of switching render targets on each draw to make a custom
> clip is enormous. There are virtually no circumstances where this will
> outperform our cached, multi-threaded software mask generator. The
> tried-and-true approach to clipping on-GPU is with analytic FPs. And
> now that we support CCPR clip FPs, there ulitmately should be very few
> clip stacks that even require a mask as long as they don't use
> deprecated SkClipOps.
> 
> Bug: skia:
> Change-Id: I79c5558c93c1b99179f1e933d029f69b14ad1ce3
> Reviewed-on: https://skia-review.googlesource.com/116724
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Chris Dalton <csmartdalton@google.com>

TBR=robertphillips@google.com,brianosman@google.com,csmartdalton@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: skia:
Change-Id: Iba289e00ba2eca7084dc8517491cfb5f6ab6266f
Reviewed-on: https://skia-review.googlesource.com/117420
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/gpu/GrReducedClip.h b/src/gpu/GrReducedClip.h
index 5447652137..c3838d8802 100644
--- a/src/gpu/GrReducedClip.h
+++ b/src/gpu/GrReducedClip.h
@@ -83,6 +83,7 @@ public:
      */
     bool maskRequiresAA() const { SkASSERT(!fMaskElements.isEmpty()); return fMaskRequiresAA; }
 
+    bool drawAlphaClipMask(GrRenderTargetContext*) const;
     bool drawStencilClipMask(GrContext*, GrRenderTargetContext*) const;
 
     int numAnalyticFPs() const { return fAnalyticFPs.count() + fCCPRClipPaths.count(); }