Add isSingleComponent bool to getConstantColorComponent

src/core/SkXfermode.cpp

Index: src/core/SkXfermode.cpp
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 8a3218fcbd0087f0d264f5550412c8a6171acf9c..1d151e4dbaa140e56cadb657d470d069ae78c696 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -799,11 +799,6 @@ public:
         }
     }
 
-    virtual void getConstantColorComponents(GrColor* color,
-                                            uint32_t* validFlags) const SK_OVERRIDE {
-        *validFlags = 0;
-    }
-
     virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE {
         return GrTBackendFragmentProcessorFactory<XferEffect>::getInstance();
     }
@@ -1216,6 +1211,11 @@ private:
         return fMode == s.fMode &&
                fBackgroundAccess.getTexture() == s.fBackgroundAccess.getTexture();
     }
+    
+    virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE {
+        inout->fValidFlags = 0;
+        inout->fIsSingleComponent = false;
+    }
 
     SkXfermode::Mode fMode;
     GrCoordTransform fBackgroundTransform;