Add XP to handle the cases where we disable color write.

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 d956cd31b08d6d5c1fbc701c000f31e0c23ac993..bb87616e74472028cac3aeafdfd51ad92987dc18 100644
--- a/src/gpu/effects/GrCoverageSetOpXP.cpp
+++ b/src/gpu/effects/GrCoverageSetOpXP.cpp
@@ -9,7 +9,6 @@
 #include "effects/GrCoverageSetOpXP.h"
 #include "GrColor.h"
 #include "GrDrawTargetCaps.h"
-#include "GrInvariantOutput.h"
 #include "GrProcessor.h"
 #include "GrProcOptInfo.h"
 #include "gl/GrGLXferProcessor.h"
@@ -68,7 +67,6 @@ GrGLXferProcessor* GrCoverageSetOpXP::createGLInstance() const {
 GrXferProcessor::OptFlags
 GrCoverageSetOpXP::getOptimizations(const GrProcOptInfo& colorPOI,
                                     const GrProcOptInfo& coveragePOI,
-                                    bool colorWriteDisabled,
                                     bool doesStencilWrite,
                                     GrColor* color,
                                     const GrDrawTargetCaps& caps) {
@@ -188,7 +186,6 @@ GrXferProcessor* GrCoverageSetOpXPFactory::createXferProcessor(const GrProcOptIn
 
 void GrCoverageSetOpXPFactory::getInvariantOutput(const GrProcOptInfo& colorPOI,
                                                   const GrProcOptInfo& coveragePOI,
-                                                  bool colorWriteDisabled,
                                                   GrXPFactory::InvariantOutput* output) const {
     if (SkRegion::kReplace_Op == fRegionOp) {
         if (coveragePOI.isSolidWhite()) {
@@ -209,6 +206,11 @@ void GrCoverageSetOpXPFactory::getInvariantOutput(const GrProcOptInfo& colorPOI,
     }
 }
 
+bool GrCoverageSetOpXPFactory::willReadDst(const GrProcOptInfo& colorPOI,
+                                           const GrProcOptInfo& coveragePOI) const {
+    return coveragePOI.readsDst();
+}
+
 GR_DEFINE_XP_FACTORY_TEST(GrCoverageSetOpXPFactory);
 
 GrXPFactory* GrCoverageSetOpXPFactory::TestCreate(SkRandom* random,