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 0023752a87cc519bd25710f925f9c8ecca1f2ed1..bd07b4f948e8dd50213b1d7d5c43e2c3a2ad3bf8 100644
--- a/src/gpu/effects/GrCoverageSetOpXP.cpp
+++ b/src/gpu/effects/GrCoverageSetOpXP.cpp
@@ -224,7 +224,13 @@ GrXferProcessor*
 GrCoverageSetOpXPFactory::onCreateXferProcessor(const GrCaps& caps,
                                                 const GrProcOptInfo& colorPOI,
                                                 const GrProcOptInfo& covPOI,
+                                                bool hasMixedSamples,
                                                 const DstTexture* dst) const {
+    // We don't support inverting coverage with mixed samples. We don't expect to ever want this in
+    // the future, however we could at some point make this work using an inverted coverage
+    // modulation table. Note that an inverted table still won't work if there are coverage procs.
+    SkASSERT(!fInvertCoverage || !hasMixedSamples);

[egdaniel, 2015/06/08 21:29:45]

Lets return NULL here if we hit this case

+
     return CoverageSetOpXP::Create(fRegionOp, fInvertCoverage);
 }