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, 19 insertions, 2 deletions

diff --git a/src/gpu/GrClipStackClip.h b/src/gpu/GrClipStackClip.h
index 05d9f18c88..aeb983468c 100644
--- a/src/gpu/GrClipStackClip.h
+++ b/src/gpu/GrClipStackClip.h
@@ -37,14 +37,31 @@ public:
     static const char kMaskTestTag[];
 
 private:
+    static bool PathNeedsSWRenderer(GrContext* context,
+                                    const SkIRect& scissorRect,
+                                    bool hasUserStencilSettings,
+                                    const GrRenderTargetContext*,
+                                    const SkMatrix& viewMatrix,
+                                    const SkClipStack::Element* element,
+                                    GrPathRenderer** prOut,
+                                    bool needsStencil);
+
     bool applyClipMask(GrContext*, GrRenderTargetContext*, const GrReducedClip&,
                        bool hasUserStencilSettings, GrAppliedClip*) const;
 
-    // Creates an alpha mask of the remaining reduced clip elements that could not be handled
-    // analytically on the GPU. The mask fills the reduced clip's scissor rect.
+    // Creates an alpha mask of the clip. The mask is a rasterization of elements through the
+    // rect specified by clipSpaceIBounds.
+    sk_sp<GrTextureProxy> createAlphaClipMask(GrContext*, const GrReducedClip&) const;
+
+    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
     sk_sp<GrTextureProxy> createSoftwareClipMask(GrContext*, const GrReducedClip&,
                                                  GrRenderTargetContext*) const;
 
+    static bool UseSWOnlyPath(GrContext*,
+                              bool hasUserStencilSettings,
+                              const GrRenderTargetContext*,
+                              const GrReducedClip&);
+
     const SkClipStack*  fStack;
 };