Use dst copies in porter duffer XP to correctly render certain blends.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/997c6358d94e188b1a7b89a4f86e24cbe0f5a164

Review URL: https://codereview.chromium.org/914003003

2 files changed, 7 insertions, 4 deletions

diff --git a/src/effects/SkArithmeticMode_gpu.cpp b/src/effects/SkArithmeticMode_gpu.cpp
index 469f5b1adb..e068c9dc37 100644
--- a/src/effects/SkArithmeticMode_gpu.cpp
+++ b/src/effects/SkArithmeticMode_gpu.cpp
@@ -304,11 +304,12 @@ GrArithmeticXPFactory::GrArithmeticXPFactory(float k1, float k2, float k3, float
 }
 
 GrXferProcessor*
-GrArithmeticXPFactory::onCreateXferProcessor(const GrProcOptInfo& colorPOI,
+GrArithmeticXPFactory::onCreateXferProcessor(const GrDrawTargetCaps& caps,
+                                             const GrProcOptInfo& colorPOI,
                                              const GrProcOptInfo& coveragePOI,
                                              const GrDeviceCoordTexture* dstCopy) const {
     return ArithmeticXP::Create(fK1, fK2, fK3, fK4, fEnforcePMColor, dstCopy,
-                                this->willReadDstColor(colorPOI, coveragePOI));
+                                this->willReadDstColor(caps, colorPOI, coveragePOI));
 }
 
 
diff --git a/src/effects/SkArithmeticMode_gpu.h b/src/effects/SkArithmeticMode_gpu.h
index 822e7bde1e..546902dd50 100644
--- a/src/effects/SkArithmeticMode_gpu.h
+++ b/src/effects/SkArithmeticMode_gpu.h
@@ -96,11 +96,13 @@ public:
 private:
     GrArithmeticXPFactory(float k1, float k2, float k3, float k4, bool enforcePMColor); 
 
-    GrXferProcessor* onCreateXferProcessor(const GrProcOptInfo& colorPOI,
+    GrXferProcessor* onCreateXferProcessor(const GrDrawTargetCaps& caps,
+                                           const GrProcOptInfo& colorPOI,
                                            const GrProcOptInfo& coveragePOI,
                                            const GrDeviceCoordTexture* dstCopy) const SK_OVERRIDE; 
 
-    bool willReadDstColor(const GrProcOptInfo& colorPOI,
+    bool willReadDstColor(const GrDrawTargetCaps& caps,
+                          const GrProcOptInfo& colorPOI,
                           const GrProcOptInfo& coveragePOI) const SK_OVERRIDE {
         return true;
     }