Only discard for XP dstCopies if we have a coverage value.

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 69b9ea417e23e473e1df4e63acd06db1e1f6f05c..02552b3bae8c7788a6c1b26a6304ee104e7141e5 100644
--- a/src/gpu/effects/GrCoverageSetOpXP.cpp
+++ b/src/gpu/effects/GrCoverageSetOpXP.cpp
@@ -29,17 +29,17 @@ public:
 
     bool hasSecondaryOutput() const override { return false; }
 
-    GrXferProcessor::OptFlags getOptimizations(const GrProcOptInfo& colorPOI,
-                                               const GrProcOptInfo& coveragePOI,
-                                               bool doesStencilWrite,
-                                               GrColor* color,
-                                               const GrDrawTargetCaps& caps) override;
-
     bool invertCoverage() const { return fInvertCoverage; }
 
 private:
     CoverageSetOpXP(SkRegion::Op regionOp, bool fInvertCoverage);
 
+    GrXferProcessor::OptFlags onGetOptimizations(const GrProcOptInfo& colorPOI,
+                                                 const GrProcOptInfo& coveragePOI,
+                                                 bool doesStencilWrite,
+                                                 GrColor* color,
+                                                 const GrDrawTargetCaps& caps) override;
+
     void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
 
     void onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const override;
@@ -108,11 +108,11 @@ GrGLXferProcessor* CoverageSetOpXP::createGLInstance() const {
 }
 
 GrXferProcessor::OptFlags
-CoverageSetOpXP::getOptimizations(const GrProcOptInfo& colorPOI,
-                                  const GrProcOptInfo& coveragePOI,
-                                  bool doesStencilWrite,
-                                  GrColor* color,
-                                  const GrDrawTargetCaps& caps) {
+CoverageSetOpXP::onGetOptimizations(const GrProcOptInfo& colorPOI,
+                                    const GrProcOptInfo& coveragePOI,
+                                    bool doesStencilWrite,
+                                    GrColor* color,
+                                    const GrDrawTargetCaps& caps) {
     // We never look at the color input
     return GrXferProcessor::kIgnoreColor_OptFlag; 
 }