Remove the need for asCoeff in SkXfermode.

src/core/SkXfermode_proccoeff.h

Index: src/core/SkXfermode_proccoeff.h
diff --git a/src/core/SkXfermode_proccoeff.h b/src/core/SkXfermode_proccoeff.h
index 88b4d34e630ffc46876779f43836725b337dcdae..4e39527b6052d8a155dc2b378ef76f18cf3c1141 100644
--- a/src/core/SkXfermode_proccoeff.h
+++ b/src/core/SkXfermode_proccoeff.h
@@ -34,6 +34,10 @@ public:
 
     bool asCoeff(Coeff* sc, Coeff* dc) const SK_OVERRIDE;
 
+    bool supportsCoverageAsAlpha() const SK_OVERRIDE;
+
+    bool isOpaque(SkXfermode::SrcColorOpacity opacityType) const SK_OVERRIDE;
+
 #if SK_SUPPORT_GPU
     virtual bool asFragmentProcessor(GrFragmentProcessor**,
                                      GrTexture* background) const SK_OVERRIDE;