Use shader based blending to clamp kPlus mode w/F16

Bug: skia:6173
Change-Id: I21042d484d9a7b3eee04aa3301d9793d00ad6908
Reviewed-on: https://skia-review.googlesource.com/48183
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/src/gpu/effects/GrCoverageSetOpXP.cpp b/src/gpu/effects/GrCoverageSetOpXP.cpp
index 267f43d..0e7dcf7 100644
--- a/src/gpu/effects/GrCoverageSetOpXP.cpp
+++ b/src/gpu/effects/GrCoverageSetOpXP.cpp
@@ -211,7 +211,8 @@
         const GrProcessorAnalysisColor&,
         GrProcessorAnalysisCoverage,
         bool hasMixedSamples,
-        const GrCaps& caps) const {
+        const GrCaps& caps,
+        GrPixelConfigIsClamped dstIsClamped) 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.