Add XferProcessor factory in GrPaint and GrDrawState.

gyp/gpu.gypi

Index: gyp/gpu.gypi
diff --git a/gyp/gpu.gypi b/gyp/gpu.gypi
index 0cef7c7be0e3a778a9cb770c9394f8a0a03078ed..1b7c9a836c7573c77c8343209d3ffedb693aea65 100644
--- a/gyp/gpu.gypi
+++ b/gyp/gpu.gypi
@@ -35,6 +35,7 @@
       '<(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/gl/GrGLConfig.h',
       '<(skia_include_path)/gpu/gl/GrGLExtensions.h',
@@ -185,6 +186,7 @@
       '<(skia_src_path)/gpu/effects/GrCustomCoordsTextureEffect.h',
       '<(skia_src_path)/gpu/effects/GrDashingEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrDashingEffect.h',
+      '<(skia_src_path)/gpu/effects/GrDefaultXferProcessor.h',
       '<(skia_src_path)/gpu/effects/GrDistanceFieldTextureEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrDistanceFieldTextureEffect.h',
       '<(skia_src_path)/gpu/effects/GrDitherEffect.cpp',
@@ -193,6 +195,8 @@
       '<(skia_src_path)/gpu/effects/GrMatrixConvolutionEffect.h',
       '<(skia_src_path)/gpu/effects/GrOvalEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrOvalEffect.h',
+      '<(skia_src_path)/gpu/effects/GrPorterDuffXferProcessor.cpp',
+      '<(skia_src_path)/gpu/effects/GrPorterDuffXferProcessor.h',
       '<(skia_src_path)/gpu/effects/GrRRectEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrRRectEffect.h',
       '<(skia_src_path)/gpu/effects/GrSimpleTextureEffect.cpp',