Add mixed samples support to XPs

src/gpu/effects/GrCoverageSetOpXP.cpp

Index: src/gpu/effects/GrCoverageSetOpXP.cpp
diff --git a/src/gpu/effects/GrCoverageSetOpXP.cpp b/src/gpu/effects/GrCoverageSetOpXP.cpp
index a0edfe71f33998eaff764948a8399cd7fbc1bae9..4f8552893513e76aabc1a660b59f59c5c37670a8 100644
--- a/src/gpu/effects/GrCoverageSetOpXP.cpp
+++ b/src/gpu/effects/GrCoverageSetOpXP.cpp
@@ -27,8 +27,6 @@ public:
 
     GrGLXferProcessor* createGLInstance() const override;
 
-    bool hasSecondaryOutput() const override { return false; }
-
     bool invertCoverage() const { return fInvertCoverage; }
 
 private:
@@ -224,6 +222,7 @@ GrXPFactory* GrCoverageSetOpXPFactory::Create(SkRegion::Op regionOp, bool invert
 
 GrXferProcessor*
 GrCoverageSetOpXPFactory::onCreateXferProcessor(const GrCaps& caps,
+                                                const GrPipelineBuilder&,
                                                 const GrProcOptInfo& colorPOI,
                                                 const GrProcOptInfo& covPOI,
                                                 const DstTexture* dst) const {