Orphan ProcXfermode, with an eye towards removing it

include/core/SkXfermode.h

Index: include/core/SkXfermode.h
diff --git a/include/core/SkXfermode.h b/include/core/SkXfermode.h
index 4af6cb43d182504f0d99a1a46f17b84da0107891..9bad1e8d37b2e9302dd3edf372c7921affe8d275 100644
--- a/include/core/SkXfermode.h
+++ b/include/core/SkXfermode.h
@@ -17,6 +17,8 @@ class GrEffectRef;
 class GrTexture;
 class SkString;
 
+//#define SK_SUPPORT_LEGACY_PROCXFERMODE
+
 /** \class SkXfermode
  *
  *  SkXfermode is the base class for objects that are called to implement custom
@@ -246,6 +248,7 @@ private:
 
 ///////////////////////////////////////////////////////////////////////////////
 
+#ifdef SK_SUPPORT_LEGACY_PROCXFERMODE
 /** \class SkProcXfermode
 
     SkProcXfermode is a xfermode that applies the specified proc to its colors.
@@ -291,5 +294,6 @@ private:
 
     typedef SkXfermode INHERITED;
 };
+#endif
 
 #endif