Revert of 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 1d151e4dbaa140e56cadb657d470d069ae78c696..8a3218fcbd0087f0d264f5550412c8a6171acf9c 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -797,6 +797,11 @@
         } else {
             return SkNEW_ARGS(XferEffect, (mode, background));
         }
+    }
+
+    virtual void getConstantColorComponents(GrColor* color,
+                                            uint32_t* validFlags) const SK_OVERRIDE {
+        *validFlags = 0;
     }
 
     virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE {
@@ -1211,11 +1216,6 @@
         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;