Add mixed samples support to XPs

src/gpu/effects/GrCustomXfermodePriv.h

Index: src/gpu/effects/GrCustomXfermodePriv.h
diff --git a/src/gpu/effects/GrCustomXfermodePriv.h b/src/gpu/effects/GrCustomXfermodePriv.h
index 0b893b8c926ad37ed2662b6003cc3c134869ea22..3dc65ada5318d6e5baafe70fd7971f6754264da4 100644
--- a/src/gpu/effects/GrCustomXfermodePriv.h
+++ b/src/gpu/effects/GrCustomXfermodePriv.h
@@ -69,11 +69,13 @@ public:
 
 private:
     GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
+                                           const GrPipelineBuilder&,
                                            const GrProcOptInfo& colorPOI,
                                            const GrProcOptInfo& coveragePOI,
                                            const DstTexture*) const override; 
 
     bool willReadDstColor(const GrCaps& caps,
+                          const GrPipelineBuilder&,
                           const GrProcOptInfo& colorPOI,
                           const GrProcOptInfo& coveragePOI) const override;