Use SkXfermode as public facing enum for GrPorterDuffXP

gyp/gpu.gypi

 # Include this gypi to include all 'gpu' files
 # The parent gyp/gypi file must define
 #       'skia_src_path'     e.g. skia/trunk/src
 #       'skia_include_path' e.g. skia/trunk/include
 #
 # The skia build defines these in common_variables.gypi
 #
 {
   'variables': {
     'skgpu_sources': [
@@ skipping 16 matching lines @@
       '<(skia_include_path)/gpu/GrRenderTarget.h',
       '<(skia_include_path)/gpu/GrResourceKey.h',
       '<(skia_include_path)/gpu/GrSurface.h',
       '<(skia_include_path)/gpu/GrShaderVar.h',
       '<(skia_include_path)/gpu/GrTexture.h',
       '<(skia_include_path)/gpu/GrTextureAccess.h',
       '<(skia_include_path)/gpu/GrTypes.h',
       '<(skia_include_path)/gpu/GrUserConfig.h',
       '<(skia_include_path)/gpu/GrXferProcessor.h',
 
+      '<(skia_include_path)/gpu/effects/GrCoverageSetOpXP.h',
       '<(skia_include_path)/gpu/effects/GrCustomXfermode.h',
       '<(skia_include_path)/gpu/effects/GrPorterDuffXferProcessor.h',
 
       '<(skia_include_path)/gpu/gl/GrGLConfig.h',
       '<(skia_include_path)/gpu/gl/GrGLExtensions.h',
       '<(skia_include_path)/gpu/gl/GrGLFunctions.h',
       '<(skia_include_path)/gpu/gl/GrGLInterface.h',
       '<(skia_include_path)/gpu/gl/GrGLSLPrettyPrint.h',
 
       '<(skia_src_path)/gpu/GrAAHairLinePathRenderer.cpp',
@@ skipping 132 matching lines @@
       '<(skia_src_path)/gpu/GrTexturePriv.h',
       '<(skia_src_path)/gpu/GrTextureAccess.cpp',
       '<(skia_src_path)/gpu/GrTRecorder.h',
       '<(skia_src_path)/gpu/GrVertexBuffer.h',
       '<(skia_src_path)/gpu/GrXferProcessor.cpp',
 
       '<(skia_src_path)/gpu/effects/Gr1DKernelEffect.h',
       '<(skia_src_path)/gpu/effects/GrConfigConversionEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrConfigConversionEffect.h',
       '<(skia_src_path)/gpu/effects/GrCoverageSetOpXP.cpp',
-      '<(skia_src_path)/gpu/effects/GrCoverageSetOpXP.h',
       '<(skia_src_path)/gpu/effects/GrCustomXfermode.cpp',
       '<(skia_src_path)/gpu/effects/GrCustomXfermodePriv.h',
       '<(skia_src_path)/gpu/effects/GrBezierEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrBezierEffect.h',
       '<(skia_src_path)/gpu/effects/GrConvolutionEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrConvolutionEffect.h',
       '<(skia_src_path)/gpu/effects/GrConvexPolyEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrConvexPolyEffect.h',
       '<(skia_src_path)/gpu/effects/GrBicubicEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrBicubicEffect.h',
@@ skipping 179 matching lines @@
       '<(skia_src_path)/gpu/gl/debug/SkDebugGLContext.cpp',
       '<(skia_src_path)/gpu/gl/debug/SkDebugGLContext.h',
     ],
     'skgpu_null_gl_sources': [
       '<(skia_src_path)/gpu/gl/GrGLCreateNullInterface.cpp',
       '<(skia_src_path)/gpu/gl/SkNullGLContext.cpp',
       '<(skia_include_path)/gpu/gl/SkNullGLContext.h',
     ],
   },
 }