Add luminance mask transfer modes.

gyp/public_headers.gypi

 # Include this gypi to include all public header files that exist in the
 # include directory.
 #
 # The list is computed by running 'find include -name *.h' in the root dir of
 # the project.
 #
 {
   'variables': {
     'header_filenames': [
       'pdf/SkPDFDevice.h',
@@ skipping 60 matching lines @@
       'images/SkForceLinking.h',
       'images/SkImageRef_GlobalPool.h',
       'images/SkImages.h',
       'effects/SkMorphologyImageFilter.h',
       'effects/Sk2DPathEffect.h',
       'effects/SkXfermodeImageFilter.h',
       'effects/SkArithmeticMode.h',
       'effects/SkMergeImageFilter.h',
       'effects/SkPerlinNoiseShader.h',
       'effects/SkLerpXfermode.h',
+      'effects/SkLumaXfermode.h',
       'effects/SkRectShaderImageFilter.h',
       'effects/SkMagnifierImageFilter.h',
       'effects/SkBicubicImageFilter.h',
       'effects/SkPorterDuff.h',
       'effects/SkBlurImageFilter.h',
       'effects/SkKernel33MaskFilter.h',
       'effects/SkTableMaskFilter.h',
       'effects/SkAvoidXfermode.h',
       'effects/SkBitmapSource.h',
       'effects/SkCornerPathEffect.h',
@@ skipping 216 matching lines @@
       'lazy/SkLruImageCache.h',
     ],
   },
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: