In order to use CSS luminance masking, we need to be able to create an instance of SkLumaXfermode w…

include/effects/SkLumaXfermode.h

Index: include/effects/SkLumaXfermode.h
===================================================================
--- include/effects/SkLumaXfermode.h	(revision 11192)
+++ include/effects/SkLumaXfermode.h	(working copy)
@@ -16,7 +16,7 @@
  *  http://www.w3.org/TR/css-masking/#MaskValues
  *
  *  The luminance-to-alpha function is applied before performing a standard
- *  SrcIn/DstIn xfer:
+ *  SrcIn/DstIn/SrcOver xfer:
  *
  *    luma(C) = (0.2125 * C.r + 0.7154 * C.g + 0.0721 * C.b) * C.a
  *
@@ -26,7 +26,7 @@
 public:
     /** Return an SkLumaMaskXfermode object for the specified submode.
      *
-     *  Only kSrcIn_Mode and kDstIn_Mode are supported - for everything else,
+     *  Only kSrcIn_Mode, kDstIn_Mode kSrcOver_Mode are supported - for everything else,
      *  the factory returns NULL.
      */
     static SkXfermode* Create(SkXfermode::Mode);
@@ -47,12 +47,14 @@
     SkLumaMaskXfermode(SkFlattenableReadBuffer&);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
 
-private:
     SkLumaMaskXfermode(SkXfermode::Mode);
 
+private:
     const SkXfermode::Mode fMode;
 
     typedef SkXfermode INHERITED;
+
+    virtual SkPMColor lumaProc(const SkPMColor a, const SkPMColor b) const;
 };
 
 #endif